Diophantine applications of geometric invariant theory 2856298656, 9782856298657


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Marco MACULAN

DIOPHANINE APPLICAIONS OF GEOMERIC INVARIAN HEORY

MÉMOIRES DE LA SMF 152

Société Mathématique de France 2017

Comité de rédaction Chrisine BACHOC Emmanuel BREUILLARD Yann BUGEAUD Jean-François DAT Marc HERZLICH O’ Grady KIERAN

Raphaël KRIKORIAN Julien MARCHÉ Lauren MANIVEL Emmanuel RUSS Chrisophe SABOT Wilhelm SCHLAG

Pascal HUBERT (dir.) Difusion AMS P.O. Box 6248 Providence RI 02940 USA www.ams.org

Maison de la SMF B.P. 67 13274 Marseille Cedex 9 France [email protected] Taris 2017

Vene au numéro : 35 € ($ 52) Abonnemen élecronique : 113 € ($ 170) Abonnemen avec supplémen papier : 162 €, hors Europe : 186 € ($ 279) Des condiions spéciales son accordées aux membres de la SMF. Secrétariat : Nathalie Christiaën Mémoires de la SMF Sociéé Mahémaique de France Insiu Henri Poincaré, 11, rue Pierre e Marie Curie 75231 Paris Cedex 05, France Tél : (33) 01 44 27 67 99  Fax : (33) 01 40 46 90 96 [email protected]  http://smf.emath.fr/ © Sociéé Mahémaique de France 2017 Tous drois réservés (aricle L 122–4 du Code de la propriéé inellecuelle). Toue représenaion ou reproducion inégrale ou parielle aie sans le consenemen de l’édieur es illicie. Cete représenaion ou reproducion par quelque procédé que ce soi consiuerai une conreaçon sancionnée par les aricles L 335–2 e suivans du CPI.

ISSN 0249-633X (prin) 2275-3230 (elecronic) ISBN 978-2-85629-865-7

Séphane SEURET Direceur de la publicaion

MÉMOIRES DE LA SMF 152

DIOPHANINE APPLICAIONS OF GEOMERIC INVARIAN HEORY

Marco MACULAN

Société Mathématique de France 2017 Publié avec le concours du Centre National de la Recherche Scientifque

M. MACULAN Institut Mathématique de Jussieu, Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris. E-mail : [email protected] Url : http://webusers.imj-prg.fr/~marco.maculan/

2010 Mathematics Subject Classification. --- Primary 14L24, 14G40, 11K60, 14G22. Key words and phrases. --- Geometric Invariant Theory, diophantine approximation, Roth’s Theorem, Berkovich spaces, height o semi-stable points. DOI. --- 10.24033/msm.460.

Partially supported by ANR research project “Positive” ANR-2010-BLAN-0119-01.

DIOPHANTINE APPLICATIONS OF GEOMETRIC INVARIANT THEORY Marco MACULAN

Abstract. --- This text consists o two parts. In the frst one we present a proo o Thue-Siegel-Roth’s Theorem (and its more recent variants, such as those o Lang or number felds and that “with moving targets” o Vojta) as an application o Geometric Invariant Theory (GIT). Roth’s Theorem is deduced rom a general ormula comparing the height o a semi-stable point and the height o its projection on the GIT quotient. In this setting, the role o the zero estimates appearing in the classical proo is played by the geometric semi-stability o the point to which we apply the ormula. In the second part we study heights on GIT quotients. We generalise Burnol’s construction o the height and refne diverse lower bounds o the height o semi-stable points established to Bost, Zhang, Gasbarri and Chen. The proo o Burnol’s ormula is based on a non-archimedean version o Kemp-Ness theory (in the ramework o Berkovich analytic spaces) which completes the ormer work o Burnol. Résumé (Applications diophantiennes de la théorie géométrique des invariants) Ce texte est constitué de deux parties. Dans la première nous présentons une preuve du théorème de Thue-Siegel-Roth (et des variantes plus récentes, comme celle de Lang pour le corps de nombres et celle with moving targets de Vojta) basée sur la théorie géométrique des invariants (GIT). Le théorème de Roth est déduit d’une ormule reliant la hauteur d’un point semi-stable et la hauteur de sa projection dans le quotient GIT. Dans ce cadre, le rôle du « lemme des zéros » présent dans la preuve classique est joué par la semi-stabilité géométrique du point auquel on applique la ormule. Dans la deuxième partie nous étudions la hauteur sur les quotients GIT. Nous généralisons la construction de Burnol de cette hauteur et nous améliorons plusieurs minorations de la hauteur de point semi-stables précédemment établies par Bost, Zhang Gasbarri et Chen. La preuve de la ormule de Burnol porte sur une version non-archimédienne de la théorie de Kemp-Ness (dans le langage de la géométrie analytique de Berkovich), qui complète le travail antérieur de Burnol.

© Mémoires de la Société Mathématique de France 152, SMF 2017

CONENS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

1. Geometric Invariant Teory and Arakelov Geometry: basic results . . . . . . . . 13 1. T F F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2. L       q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2. Diophantine approximation on P via Geometric Invariant Teory . . . . . . . . 1. S    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. F  F F   M T . . . . . . . . . . . . . . . . . . . . . . . . . 3. U     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. U      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. E   :      . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. S  P  P   W  . . . . . . . . . . . . . . . . . . . .

27 27 36 44 48 54 60

3. Kemp-Ness Teory in Non-Archimedean Geometry . . . . . . . . . . . . . . . . . . . . . . . 1. S     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. P     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. KN  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. M  GI q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

69 70 76 90 102

4. Heights on GI quotients: urther results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. S     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. E     q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. T   B, G  Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. L       q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

113 114 120 129 136

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

INRODUCION

I   , R’ T          R           ,         pq  Q    p         q q

 p q   . T     R’ T       T. T        “”  f                :                  “”       . T    R (   T, S  G’)          . O   ,     D —       R’ T —    (  “D’ L”)       :     ,        . T    D’ L         E V [28];  N [50]              F’ P T  “”    . T        D’ L    B     [7]:                        B. U      P T, F  W [30]      S’ S T,      . T Z L,   R  S,    . T           (  [29]). T               :           D’ L (   P T);                   P T. I    O [53]  S [65] V   [69]     R’ T —  “  ” —           . I        S’ S T. H      B  G [8, T 6.5.2  §6.6]   q    R’ T f     “  ”    S’ S T.

CONENS

7

T      G I T    (    A )             . B [20]       GI q                             . B [12], [13], Z [75]  S [64]           (   )              (e.g.  ,  …). G [32]        B  Z          GLn . C [22]              —     RR [56]   [67] —                 . I      ,                ()                 x       x n   a       an   P Kn  P K ′n     v  ( K      K ′       ). T  ,         ,       n    B [7, T 2],        R’ T   . L        . F                 . I C 1       G I T        R’ T. T          C 4,                    R’ T  C 2. I        C 3  4         . I C 2   R’ T (     )    q   F F  C 2 (     “ ”). I C 3         KN [46]     . I C 4        q   ( )        C 1. A                . I C 2     C 1    2.3,   C 4     C 3     1. W      .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

8

CONENS

Acknowledgements T             J.B. B. I               . D       I        : I   A. CL, A. D, C. G, M. N  A. T. F, I                    q    .

MÉMOIRES DE LA SMF 152

CONVENIONS

H             . 1. — F   A     n,  An  HA An  A  T   PA    A   A  PA  PS A 

R ,  M   A   ,  M   HA M A  PM  PS M   2. — L A   , M   A  n    . S M n  M n  HA M A n  3. Hermitian Norms. — L E, F       q     ∥∥E , ∥∥F     ⟨  ⟩E , ⟨  ⟩F . L r    . ▷ O    E C F  ∥∥E F         ⟨v  w v ′  w ′⟩E F  ⟨v v ′⟩E  ⟨w w ′⟩F

 v v ′  E  w w ′  F . ▷ O  r    Sr E  ∥∥Sr E   q        E r  Sr E. I e       en      E,  n  C E,   n    r       r n    r       rn  r :       r ∥e r     enr n ∥Sr E  r    r   r n   r      rn  T           :  f  Sr E  д  Ss E,  ∥ f д∥Sr s E  ∥ f ∥Sr E ∥  д∥Ss E  L       ∥∥Sr E         :  f  Sr E,  f x r ∥ f ∥    r  ∥ f ∥S E   ,x E ∥x ∥E   ▷ O  r    r E  ∥∥r E           ⟨v       vr  w       w r ⟩r E   ⟨vi  w j ⟩E  i j       r  v       vr  w       w r    E.

CONENS

10

W   H q 1 : (1)

∥v       vr ∥r E 

r ∏ i 

∥vi ∥E 

T   ∥∥r E  no  q          E r  r E,    r    q  ( [22, L 4.1]). ▷ F    ϕ  E  F  ϕ      (      ∥∥E  ∥∥F ). O    HC E F   ∥∥HE F           ⟨ϕ ⟩HE F   ϕ ◦   

 ϕ  HC E F . I e       en      E,  ∥ϕ ∥HE F   ∥ϕe  ∥F      ∥ϕen ∥F 

W     E  C F  HC E F   .

4. Non-archimedean norms. — L K               o     . I            o  K      . M ,     o E   E  E o K        :   v  E    ∥v ∥ E       K   v  E 

T  ∥∥ E           o :  ,  ϕ  E  F        (.  )    o    ∥∥ E   E  Eo K (.   ∥∥ F   F  Fo K)       ∥∥ F  F (.   q    ∥∥ E  ϕ,  ,     w 



ϕ v w

∥v ∥ E

   w  F .) F    r  ,      Sr E (.     r E)          r    Er      Er  Sr E (. Er  r E). I ,     (. H q ). 5. Normalisation o places. — F    K  oK       VK      . I v     K,  Kv     K    v  Cv        Kv (   q    v). A   v   p      p v  p Kv Qp   1. T q  H’          E    H H’ q   .

MÉMOIRES DE LA SMF 152

ACKNOWLEDGEMENS

11

6. Hermitian vector bundles and Arakelov degree. — L K    , oK      VK    . A    E       oK     E ,       K  C,    ∥∥ E      E  E  C. T          . F   v  VK  ∥∥ Ev       Kv   Ev  E oK Kv . I E, F      oK ,  homomorphism o hermiian vecor bundles ϕ  E  F     oK   ,      K  C,    :  ,   v  E  C, ∥ϕv∥ F  ∥v ∥ E 

I L     ,         ,  degree  ∑  L   #Ls L   ∥s ∥ L  



v VK 



  K C

 ∥s ∥ Lv 

v VK 

Kv  R  ∥s ∥ Lv 

 s  L  . I       ,    P F,        s. F      E      E E  E   ▷  degree:   E  ▷  slope:    E    E ▷  maximal slope:     E      F , F E

         F  E          E.

Proposition (S q, [14]). — Le E F be oK -hermiian vecor bundles and le ϕ  E oK K  F oK K be an injecive homomorphism o K-vecor spaces. Ten, ∑    F   ∥ϕ ∥ v     E   where, or every place v  VK ,

v VK

∥ϕ ∥ v  

,s  Ev

∥ϕs∥ Fv  ∥s ∥ Ev

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CONENS

12

7. Height unction with respect to a hermitian line bundle. — L K    , oK      X    oK . ▷ A hermiian line bundle

L  L ∥∥ L   K C 

       L  X ,    K  C,    ∥∥ L      L X C . T  ∥∥ L   K C      . L K ′      K, oK ′      P  K ′  X. B     ,   P     oK   P  S oK ′  X

T  oK ′          L:       oK ′    P L.  P L 

▷ T heigh o P wih respec o L  h L P 

   L  P K ′  K

M ,  s  H   X L        P, ∑ K ′  Kh L P   # P LsP P L   ∥s ∥ L P   K C  K ′,

T   h LP       h L  XQ  R   heigh uncion wih respec o L.

MÉMOIRES DE LA SMF 152

    

CHAPER 1 GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY: BASIC RESULS

I         G I T ( F  F,  T 1.6)      C 2    “ ”      R’ T:                     GI q. I                 q ( T 2.1). E        C 4     q,         :           . W                R’ T   C 2. 1. Te Fundamental Formula L K      oK    . 1.1. — L X      oK        oK   1 G   L   very ample G    X. T    E   X L        G. T    G   P E      OE   G. T   j  X  P E     j  OE  ≃ L  Gq. 1. O     k    G — i.e.     f k   —     reducive             . O    S    G     reducive ( G   S -reducive group)      : 1) G  f,       S ; 2)   s  S ,  s  G s  G S s      ( s            s). E  S    GLn S , SLn S   . I     oK   SLn oK   . T      [9, C IV]        [34], [24]       .

14

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

1.2. — A  x  X     semi-sable   ,   f  d  ,  G   s   X Ld       x.  d C  oK      A  d    X L . A     S [63, II.4, T 4]     AG   X Ld  G d 

 G  A   oK        Y  P AG    q     X     X (        G     L). F      

X G (   X L G      ). L   X  Y   q . S Y    ,   f   D  ,       MD  Y   Gq      ϕ D    MD  LD X 1.3. — F     K  C  ∥∥ E      E  C             G C. S      ∥∥ E   K C     .

L ∥∥ O   FS      OE       ∥∥ E   ∥∥ L     L. D  L      X   L      ∥∥ L   K C . F  y  Y C   t  y  MD    ∥t ∥ MD  y   ϕ D  t LD  x x  X C  x y

Lemma 1.1. — Le f   Y MD  be a global secion.

 Tere exiss a unique G-invarian global secion f   X LD  which vanishes idenically on X  X and such ha ϕ D   f   f X .  For every complex embedding   K  C, 

y  Y C

∥ f ∥ MD  y 



x  X C

∥ f ∥ LD  x

I , ∥t ∥ MD  y     t  y  MD ,    ∥∥ MD         MD . Proo. — 1) I        Y  MD . 2) I   1).

MÉMOIRES DE LA SMF 152



1. HE FUNDAMENAL FORMULA

15

1.4. — L M D        Y  h M D      M D ( [8, 2.7.17]). D    h M D Q    h   X L G   Q  Y Q  D (    D).

Lemma 1.2. — h   X L G  .

Proo. — L D    MD      t       t N   Y MD          . L K ′      K,  Q   K ′  Y  Q   oK ′   Y       . T  i       N    ti     Q. B    ,   ∑  ∥ti ∥ MD  Q K ′  Qh M D Q   # Q MD Q ti  Q MD   ′

  K  K



  K ′ C

  ∥ti ∥ MD  y

  K C y  Y C

I f      i       N     K  C   ∥ti ∥ MD      Y C. T   L 1.1 (2)    . □ Remark 1.3. — P  L            ∥∥ MD   . T                      . A         C 3 ( T 1.1). I         KN ( K [48, C 8, §2], B [20]  S [62, C 5]). A  (     )        Z [75, T 4.10]. 1.5. Instability measure. — L v     K. I v     ∥∥ Lv (. ∥∥ MD v )            L (. MD ) 2 . F  Cv  x  XCv   v-adic insabiliy measure  v x    

д  GCv 

∥д  s ∥ Lv д  x    ∥s ∥ Lv x

  . T        s. I x   s       jx  P E Cv , x  L 

v x  



д  GCv 

∥д  x ∥ Ev  ∥ x ∥ Ev

2. L x   Cv   X. S X  ,  Cv  x     ov   x  X,  ov       Cv . T    x L    ov    :    s  . E   s  x  L      q   s  s     Cv . S ∥s ∥ Lv x    v 

T        s    x L. S  [8, E 2.7.20].

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

16

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

Proposition 1.4. — Le v be a place o K. For every Cv -poin x  X Cv  and every non-zero secion t   x MD , ∥t ∥ M v  x   v x     D D ∥ t ∥ LD v x

Proo. — I            ∥∥ MD   G   . S  v  . U      MD     MD   . L y   x   y  Yov   q ov    Y   y       ( ov       Cv ). U   t     t      ov  y MD   ∥t ∥ MD v y  . S MD      ,   f   Y MD   ov   y f  t. A  P 1.1,      f  q   G   f   X LD   ov     X . F д  GCv . S   f  , ∥  f ∥ LD v д  x  ∥ f ∥ LD v д  x  

  ∥t ∥ MD v y     ∥ t ∥ LD v д  x  ∥t ∥ MD v y.      д  GCv , v x  

∥ t ∥ LD v д  x ∥t ∥ M v y       D     D D ∥ t ∥ LD v x д  GCv  ∥ t ∥ LD v x



Remark 1.5. — F    v,           P   q    x    x    v  , i.e.     F v     XoK F v     GF v  ( F v      Cv ). I C 3        :  ,   q     x    (  T 1.16). 1.6. Fundamental ormula. — S    : heorem 1.6 (F F). — Le P  XK be a semi-sable poin. Ten or almos all places v  VK he insabiliy measure v P is zero and ∑     h L P  v P  h M D  P  D K  Q v V K

I    T 1.6    C:

Corollary 1.7. — For every semi-sable poin P  X K, ∑    v P  h   X L G  h L P  K  Q v V K

Remark 1.8. — O      C 3  4      q      F F     (         “F F”). F ,  T 1.5  C 4.

MÉMOIRES DE LA SMF 152

2. LOWER BOUND OF HE HEIGH ON HE UOIEN

17

I   ,       B [20, P 5] (  C 1.6  C 4). 2. Lower bound o the height on the quotient 2.1. Statement o the lower bound. — L E   E      En    n  oK       . L F   oK       GL E  GL E  oK    oK GL En   GL F  ,  ,    oK  ,   uniary, i.e.,      K  C,       U E  U∥∥ E       U∥∥ En    GLd C

    ∥∥ F .

heorem 2.1. — Wih he noaion inroduced above, le b  b      bn  be n-uple o inegers and   Eb      Enbn  F a homomorphism o hermiian vecor bundles, generically surjecive and GL E-equivarian. Ten, n n  ∑  ∑ bi    Ei   bi    Ei  h  P F  OF SL E   i  i 

where OF  is equipped wih he Fubini-Sudy meric given by F and SL E is he oK reducive group SL E  oK    oK SL En .

H,  i       n   bi , Eibi   oK  Eibi  Eibi    bi       . A          C 4 ( T 1.11). T  q                Ei   (          R’ T). Remark 2.2. — T      [22, T 4.2]    :    C      K P  P F , n n ∑ ∑ h OF  P  bi    Ei  bi    Ei    i  i  C’     T 2.1    q   C 1.7   h OF  P  h  P F  OF SL E 

Remark 2.3. — I    T 2.1            bi  . I,    bi     ,   ,   i       n,  Ei  bi   ′ Ei  Ei  SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

18

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

S GL E′  GL E′       GL En′ . I

  Eb      Enbn  F

            T 2.1,        GL E′       ′  E′

 b 

     En′

 bn 

SL E′

 F

 SL E   SL E′       SL En′    T q          MD   . I ,     h  P F  OF SL E  h  P F  OF SL E′  P F 

T           T 2.1    b      b N  . Invariant theory or a product o linear groups 2.2. — L k   . L n        E  E       En   n   k    . D GLE  GLE   k    k GLEn  SLE  SLE   k    k SLEn 

Deinition 2.4. — L F    k    . A , i.e.    k ,   GLE  GLF      homogeneous o weigh b  b      bn   Zn ,   k S   S t       tn  Gm S, t   E      tn  En   t b    tnbn  F 

Proposition 2.5. — Le   GLE  GLF  be a homogeneous represenaion o weigh b  b      bn  and suppose ha he subspace o SLE-invarian elemens o F is non-rivial. Ten:  or every i       n he dimension ei o Ei divides he ineger bi ;  or every k-scheme S, any S-poin д      дn  o GLE and any SLE-invarian elemen w o F : (2.1)

д      дn   w  д b e    дn bn en  w

Proo. — T                . □ 2.3. — F    N   SN      N  ( N  ,  S  ∅ ). I E   k    SN    N    E N  . E,    SN     x       x N    E,   x       x N   x        x  N  

Deinition 2.6. — F N  Z          k S N   Ek E N     E N . MÉMOIRES DE LA SMF 152

2. LOWER BOUND OF HE HEIGH ON HE UOIEN

19

2.4. — L b  b      bn    n   . T  Sb  Sb      Sbn 

    k  E b  E b      Enbn . T k  GLE      k  Ek E b   Ek E b  k    k Ek Enbn 

T  GLE  GLEE b             . P 2.52)       EE Db         GLE      SLE   . Deinition 2.7. — T     Sb  E b      n b  k i  kSbi   EE     Eb .

T    Eb         EE b . T F M T  I T f          (c. [71, C III], [22, T 3.1, C]  [2, A 1]):

heorem 2.8 (F M T  I T). — Suppose ha he characerisic o k is zero. Te subspace o SLE-invarian elemens o he k-vecor space EE b  is he image o he homomorphism  Eb . Deinition 2.9. — W       ei  bi   i       n. C    k    bi  Ei  bi ei  Eibi Ei bi  E Ei        :   bi  Ei  bi ei E Ei Eibi  Eiei bi ei  Ei  bi ei

Eibi

  bi ei Eibi  Ei   Ei 

         . S Eb  Eb      En bn .

Corollary 2.10. — Suppose ha he characerisic o k is zero. Le F be a non-zero k-vecor space o nie dimension and   GLE  GLF  be a represenaion. Le b  b      bn  be a n-uple o non-negaive inegers and n ⊗ ϕ Eibi  F i 

be a surjecive and GLE-equivarian homomorphism o k-vecor spaces. Te represenaion  is homogeneous o weigh b  b      bn  and i he subspace o SLE-invarian elemens o F is non-zero: 1) For every i       n he dimension ei o Ei divides he ineger bi .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

20

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

2) Te subspace o SLE-invarians o F is he image o he homomorphism ϕ ◦ Eb ◦  Eb   

n ⊗ i 

kSbi  

n ⊗ i 

Ei  bi ei  F 

T       F M T  I T  : Remark 2.11. — I                  E  G    unique Gq  R E  E  E G (  R ). T q         :   Gq     E  F     G   R F ◦    ◦ R E . I ,        ϕ  E G  F G   . F ,   [49, . 182]  [48, C1, §1]. Non-hermiian norms and ensor produc. — I             . T      [36]         [33, N , . 33]    . L N          i       N  Vi           ∥∥Vi . L ∥∥Vi      Vi . D  V    V      VN . Deinition 2.12. — T          V     ,  v  V ,  ∥v ∥V  



ϕ i Vi   i   N

∥v ∥V    

R {∑

 

ϕ       ϕ N v , ∥ϕ  ∥V    ∥ϕ N ∥VN

∥v   ∥V    ∥v  N ∥VN  v 

R ∑

 

} v       v N 

T   V q    ∥∥V    V      VN . A,   V q  ∥∥V     V      VN . I   ∥∥Vi    V      VN     V        . Proposition 2.13. — Wih he noaion inroduced above:  Te -norm ∥∥ resp. he  -norm ∥∥  is he smalles resp. he bigges among he norms ∥∥ on V such ha, or i       N and vi  Vi ,   ∥v       v N ∥  ∥v  ∥V    ∥v N ∥VN  . ∥v       v N ∥  ∥v  ∥V    ∥v N ∥VN  and, or i       n and ϕ i  Vi ,

∥ϕ       ϕ N ∥   ∥ϕ  ∥V    ∥ϕ N ∥VN 



. ∥ϕ       ϕ N ∥ 

where ∥∥  denoes he operaor norm induced by ∥∥ on V  . MÉMOIRES DE LA SMF 152

  ∥ϕ  ∥V    ∥ϕ N ∥VN 

2. LOWER BOUND OF HE HEIGH ON HE UOIEN

21

 ∥v ∥V   ∥v ∥V   or all v  V .

 (D) Te isomorphism V  ≃ V C    C VN induces he ollowing isomeries:  V      VN   V      VN 

 V      VN   V      VN 

 (F) For every i       N le Wi be a nie-dimensional complex vecor space equipped wih a norm ∥∥Wi and le ϕ i  Vi  Wi be a linear map decreasing he norms. Ten, he induced maps ϕ       ϕ N  V      VN  W      WN  ϕ       ϕ N  V      VN  W      WN  decrease he norms.  Le L be a normed vecor space o dimension . Ten,   V      VN  L  V      VN  L   V      VN  L  V      VN  L

Skech o he proo. — P 1), 4)  5)       .  B ,   i       N   vi  Vi        N N ∏ ∏ ∥vi ∥Vi  ∥vi ∥Vi  ∥v       v N ∥       1).

i 

i 

 F  1)  2)  .



Proposition 2.14. — Le V and W be nie-dimensional normed vecor spaces. Te operaor norm on HC V W  coincides wih he -norm on V  C W hrough he canonical isomorphism  V  C W  HC V W  Proo. — T  T [36, §1.1, Tè 1]  E  V , F  C  G  W .



Remark 2.15. — L L      . I     P     L  L ≃ C    L  L      C. Proposition 2.16. — Le W be an hermiian vecor space and le r   be a posiive ineger.  Endow he exerior powers r W wih he hermiian norm dened in § 3 on page 9. Ten he  canonical map   W  r  r W decreases he norms. SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

22

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

Proo. — F   w  W r    w  H q (1)   10  ⟨ w  w⟩ Ei   

R ∑

   R ∑

   R ∑

 

   .

R

  w  

     w  r 

⟨w        w  r  w        w  r ⟩ Ei ∥w   ∥Ei    ∥w  r ∥Ei  ∥w   ∥Ei    ∥w  r ∥Ei 

∥w   ∥Ei    ∥w  r ∥Ei

 □

Applicaion o he lower bound o he heigh on he quoien 2.5. — L        T 2.1       bi   . D  Y  q     P F  SL E ,   f  D,  M D      Y   OFD. F D   MD   . 2.6. Application o the First Main Teorem o Invariant Teory. — A  Y  . S    K         ,       

F  Eb  Eb oK    oK Enbn 

F  i       n   Ei  K  Ei oK K   E b  K  E b K    K Enbn . T   SLE   SD F    MD   . T   i       n   ei  K Ei  Dbi . C      E Db    E Db ( D 2.7  2.9)   : ϕ  E Db  SD E b 

 E Db  E Db K    K EnDbn .

Lemma 2.17. — For every i       n le  i  Ei  be non-zero.  A se o generaors o he SLE-invarian elemens o he vecor space   SD E b   PE b  OD

is given by he image hrough ϕ ◦  o he elemens Db e 

f       

Dbn e n

     

where         n  ranges in SDb  SDb      SDbn . MÉMOIRES DE LA SMF 152



2. LOWER BOUND OF HE HEIGH ON HE UOIEN

23

 Trough he idenicaion  Y MD  oK K ≃ PE b  ODSLE  :   { ∑ }        ϕ ◦ f     h  P Eb  OFSL E   MD v D  SD b  v V YCv  K

Proo. — 1) T    q  C 2.10 (    SD E b   SLV q  ϕ). 2) L Q  YQ         K ′  K. S MD   ,   (1)     SD b     SLE  ϕ ◦ f   —       MD —     Q. B    : ∑   h MD Q    ϕ ◦ f   M v Q ∑

v VK



v VK

D

 



y  YCv 

       .

  ϕ ◦ f   M

Dv

y



2.7. Size o the invariants. — C  oK 

EDb  EDb      EnDbn 

   E Db (. E Db )  oK  EDb       K  C    ∥∥       e n  Dbn e n  E e   Db e       En  

(.     ∥∥   ). C  oK  EoK  EDb        K  C     ∥∥   E   EDb   H E Db  E Db 

D    oK   E   EDb . F    K  C      SD  Eb   C      ( § 3   9). Lemma 2.18. — Wih he noaion inroduced above, he map E Db ◦ ϕ denes an homomorphism o oK -modules n ⊗ ϕ ◦   E   EDb    Ei   Dbi ei  SD  Eb  i 



which decreases he norms.

Proo. — T     E Db ◦ ϕ       oK   . T  ϕ ◦          : 1) E Db  SD  E b ; n n  ⊗ ⊗  2) E Db   Ei   Dbi ei  E Db ;  Ei   Dbi ei  i 



i 



SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 1. GEOMERIC INVARIAN HEORY AND ARAKELOV GEOMERY

24

  3)   Ei ei   Ei ;

4) E   EDb   E Db 

n ⊗ i 



 Ei   Dbi ei



.

F    K  C       : ,  1)               § 3   9      ;  2)   P 2.135)  R 2.15;  3)       Ei   ei ≃  Ei ei    P 2.133)  P 2.16;  4)   3)  P 2.14. □ Lemma 2.19. — Le         n   SDb . For every   K  C:  ∥ ∥   e Db    e NDb N 

Proo. — F  i       n  vi       viei      Ei . C   R     R  r i j    i  n   j  Dbi        r i j  ei   i j. F  R  R  v R 

ei n Db i e i ⊗ ⊗ ⊗ i 

j 

 

vir i j ei  

n Db i e i ⊗ ⊗ i 

j 

vir i j ei       vir i j ei ei 

T  v R  R  R      EDb . F  T  EDb   T  R  R TR v R . W  : ∑ TR    ∥T ∥   TR  ∥T ∥  F  R  R 

R R

R R

 R  r ii j  i j 

 B       T    T   R  R TR v  R  . T   ∥ T ∥  ∥T ∥    ∥ T ∥ ∥T ∥ R  R TR  { }  #R  e Db    enDbn        ∥T ∥ ∥T ∥  T , T , T ,    R  R TR  (      T 



R  R v R ).



2.8. End o the proo o Teorem 2.1. — F  i       n   i  Ei   . F          n   SDb  n   ⊗ Db e Db e Ei  Dbi ei  f                 n n  EE Db   i 

MÉMOIRES DE LA SMF 152

2. LOWER BOUND OF HE HEIGH ON HE UOIEN

25

S         ϕ ◦        oK ,     v, n ∏ Db e ∥ i ∥ iEi vi   ∥ϕ ◦ f  ∥ MD v y  y  YCv 

i 

A  L 2.18  2.19      K  C: n ∏ Db e  ∥ϕ ◦ f  ∥ MD  y  ∥ϕ ◦ f  ∥   ∥ ∥   ∥ i ∥ iEi i y  YC





e Db    e NDb N 

n ∏ i 

i 

Db e

∥ i ∥ iEi i 

A  L 2.17,   K  Qh  P Eb  OFSL E  n   ∑ bi ∑  ∥ i ∥ Ei v   e b    e bNN  e i v V i  K

bi  ∑  bi   Ei   Ei  ei  i  n

 Ei ei .        Ei   



SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2 DIOPHANINE APPROXIMAION ON P1 VIA GEOMERIC INVARIAN HEORY

I     R’ T (  )      G  I T   C 1. L         . I S 1      R’ T          ( M T,  T 1.12). M ,    R’ T      q     ( M E L B,  T 1.7)          M T      . I S 2      G I T      . A            ,     F F    M T. T   (           )      S 3  4. F,  S 5,       ,           F F. O      H D D’ L  EVN (T 2.2). W               W. T     “GI ”    T  DG’.

1. Statement o the results 1.1. Roth’s Teorem with moving targets and the Main Eective Lower Bound 1.1.1. Heigh and disance on he projecive line. — I                  . Deinition 1.1. — 1) F  K x  x   x       PQ  absolue logarihmic heigh  ∑   ∥x   x  ∥ v hx  K  Q v V K

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

28

 VK       K ,    v,    x  v  x  v   ∥x   x  ∥ v     x  v  x  v 

 v    v  

2) L K      v  VK    K. T v-adic spherical disance  P  ,  Cv  x  x   x    y  y  y ,  v x y 

x y  x y v    ∥x   x  ∥ v ∥y  y ∥ v

3) L x y  K  P . T v x y         v  K. F   S  VK (  )  ∑   v x y  R   S x y  v S

I S  v     v x y.

Proposition 1.2 ( [8, T 2.8.21]). — Le x y be disinc K-raional poins o P . Ten,  V x y  hx  hy K  Q K Deinition 1.3. — L a     P      K ′  K, S  VK     VK    v  S  v  K ′  Cv   K . D  a v   Cv   P   v  : ∑ S a x  v a v   x v S

1.1.2. Roh’s Teorem wih moving arges. — I         R’ T   : heorem 1.4. — Le K be a number eld, S  VK a nie subse, K ′ a nie exension o K and    a real number. For every place v  S x an embedding v  K ′  Cv which respecs K. Tere is no sequence o couples x i  ai  wih i  N made o a K-raional poin x i o P and a K ′-raional poin ai o P disinc rom x i saisying he ollowing properies: 1) he sequence hx i  is unbounded; 2) hai   ohx i  as i goes o inniy; 3) or all i  N he ollowing inequaliy is saised:  S ai  x i   hx i  K  Q V’    R’ T      ,            K:

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE RESULS

29

heorem 1.5 (c. [69, T 1]). — Le K be a number eld, S  VK a nie subse, q   a posiive ineger and    a real number.  q  Tere is no sequence o q  -uples x i  ai      ai  (i  N) made o pairwise disinc 1 K-raional poins o P saisying he ollowing properies:  

1) or all        q, hai   ohx i  as i goes o inniy; 2) or all i  N he ollowing inequaliy is saised: q ∑    S ai  x i   hx i  K  Q  

T 1.5  T 1.4       K   G     K ′  K     ai         ai . W                   . L        q          q  P 1.2,               x i         ai . H  q                 . 1.1.3. Main Eecive Lower Bound. — A  ,          R’ T      R’ T               —         . T            K  x       x n     v      a       an . A               B [7],        . T     “M E L B”              G I T. I         r       r n :               P n .                R’ T: Deinition 1.6. — L q n        t          . 1) C   ∆n t         n    n         n  t . 2) L tqn     n   q       q  ∆n tqn    

       L   Rn . T  tqn      n      .  

1. i.e.   i  N   a i

 

, ai

 

   ,     x i , a i

         q.

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

30

3) L Rqn     q        q    n n       Rqn  

4) F  n     r  r       r n   r   r       r n .

W       M E L B (c. [7, T 2]  n  ):

heorem 1.7 (M E L B). — Le K ′ be a nie exension o K o degree q   and le S  VK be a nie se o nie places. Le n   be a posiive ineger, le     n be a real number and le r  r       r n  be an n-uple o posiive real numbers such ha r i r i   Rqn   or all i       n  . Ten, or all i       n and or all couples x i  ai  made o a K-raional poin x i o P and a K ′-raional poin ai o P such ha Kai   K ′, he ollowing inequaliy holds: { { }} ∑      r i v ai  x i  tqn   ′   K Cv i  n K  Q v S  n n   q  ∑  q∑ n r i hx i   r i hai      q      r   i   i  where, or every place v  VK , he embeddings   K ′  Cv are mean o be K-linear.

Remark 1.8. — W          M E L B  . F ,        R 1.13   M E L B        . A     R’ T             . 1.1.4. Deducing Roh’s Teorem rom he Main Eecive Lower Bound. — L     M E L B (T 1.7)  R’ T    (T 1.4). L              R                ( [47]). T       R’ T  . Lemma 1.9. — Le q n   be posiive inegers. Ten,  tqn    n   n  q In paricular,

  n

n   tqn 

Proo. — A  [8, L 6.3.5]        :    ∆n    n  n   T      

MÉMOIRES DE LA SMF 152

 

 tqn n.



1. SAEMEN OF HE RESULS

31

Proo o Teorem 1.4. — A        q x i  ai i N        T 1.4. U    q       K ′,    Kai   K ′   i  N  q  K ′  K  . F       . B    (  “M’ ”,  [8, 6.4.2])      I   N  ,    v  S        v  ,   i  I  ,     S ai  x i   vS ai  x i   v ai  x i    v  #S (     v ’   )  ∑  v     v S

U    q x i  ai i I              i  N.    n  ,       n     r        T 1.7. A       x i  ai   i       n  ,    v  S, { { { }} }   v   r r   a  x     a  x   i v i i v i i i ′   K Cv

 

i  n

i  n

n n   n ∑ ∑  r i hx i   r i qhai   C   q   i  i  { } ∑   r i v ai  x i  tqn    i  n K  Q v S { }   tqn      r i S ai  x i   i  n K  Q   C   q   . B ,   i       n,



,

S ai  x i   K  Qhx i 

n n { }    n ∑ ∑  r i hx i     q  r i hx i   r i qhai   C  i  n  i  i 

tqn     

S  x i ’         hx i  hx i       (  Rqn  ). T n r      r i hx i   r j hx j    i j       n. D   q  r hx  :

n  q ∑ hai  n r  C tqn        q  n     i  hx i  r  hx  

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

32

 n S hai   ohx i   i       hai     hx i . T   r i r i     hx       . T,   n  tqn        q  n

L        n   ,   L 1.9, n       n tqn        .



1.2. Statement o the Main Teorem 1.2.1. More combinaorial daa. — I               . Deinition 1.10. — L q n     , r  r       r n    n      t      . 1) C     Rn : n { } ∏ ⃞ r          n   Rn     i  r i   i       n   r i  {

∇r t         n   ⃞ r { ∆r t         n   ⃞ r

   r    r

i  } n t  rn } n  t  ⃞ r  ∇r t rn

A Z           Zn :  ⃞ rZ , ∇rZ t  ∆rZ t. F r         ⃞ n , ∇n t  ∆n t. 2) I n   L   Rn ,   n   n  R,    n t      n       n 

3) D qr 

n  ∏ i 

∇n t 

  

i  j n

{r } j

ri

∆n t 

 q    

4) D  uqr t  q     n   { { } }  ∆n uqr t      qr  q  ∆n t    

Lemma 1.11. — Te uncion  n   n  R is sricly concave 2 . Moreover he ollowing properies are saised: 2. T ,   t   t    n      ,  n  t      t      n t        n t  

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE RESULS

1) For all t   ,  n t  2)  n t   or all t   n;

33

tn  t    n n

3)  n n  t   n t or all t   n;

4) Te uncion  n is increasing on   n and decreasing on   n n. Proo. — S 1)  3)       . W n     1)        . F n         n          t    n t   n t  n    n  

2) F   n    n n        n . 4) F  3)       n .



1.2.2. Main Teorem. — K    ,           : heorem 1.12 (M T). — Le K ′ be a nie exension o K o degree q   and le S  VK be a nie subse. Le n   be an ineger, t a  t x   non-negaive real numbers and le r  r       r n  be an n-uple o posiive real numbers. I he ollowing inequaliy is saised, (SS)

 n uqr t a    n t x   qr 

hen, or all i       n and or all couples x i  ai  made o a K-poin x o P and K ′-poin ai o P such ha Kai   K ′, he ollowing inequaliy holds: { { }}  ∑       r  a  x    q  ∆n t a  t a i v i i   K ′ Cv i  n K  Q v S 

 Cqr t a  t x  where 

Cqr t a  t x  



n ∑ i 

∇n t x 



r i hx i   q Cqr t a  t x 

n ∑ i 



r i hai   Cqr t a  t x r 

    n   q  ∆uqr t a    n t x  

   q  ∆n t a   q  ∆uqr t a    n t x       Cqr t a  t x    ∆n uqr t a      ∇n t x     q  ∆n t a   q  Cqr t a  t x 

T 1.12      (SS)        ( ,  n uqr t a    n t x   qr   )    q  ∆n t a    . T       T 1.12        . T               ,      q  ∆n t a    , T 1.7  T 1.12      ,                .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

34

Remark 1.13. — T  Cqr t a  t x        T  1.11  C 4   T 2.1  C 1      M T.  D  ,    T 1.12   Cqr t a  t x         ∆n uqr t a      ∇n t x     q  ∆n t a   q 

(  R 2.8).

1.3. From the Main Teorem to the Main Eective Lower Bound. — I    M E L B (T 1.7)     M T 1.12.  n S r i r i   Rqn     i       n  ,  qr    .

1.3.1. Choice o he parameers. — T M E L B    T  1.12  t a  tqn   W  uqr    uqr tqn  . Lemma 1.14. — Wih he noaion inroduced above: uqr      qr  n, hence uqr    ; 1)  ∆n   n  2)   n     qr  n ; ∆n  uq r  

3)  n  uqr    qr ;

 n uqr    qr   n  n . 4)  n 

Proo. — 1) B    n  tqn    . T,     ∆n uqr      qr   n

S  ∆n t  t n n  t      n uqr    n  qr 

2) T   uqr     (1)    n uqr  n  n  n   n     qr  n  n n   ∆n  uq r    n C   nn       n  . 3) F       L 1.111),     n uqr      qr    n  qr    n  n

      qr . 4) S  3).

MÉMOIRES DE LA SMF 152



1. SAEMEN OF HE RESULS

35

F        t x ,  ,        (SS)   . M ,     n       n n,    q   w qr      n n   uqr     n w qr    qr   n 

Lemma 1.15. — Wih he noaion inroduced above:   1)  ∇n w qr     ;  2)   n   ; ∇n w q r  

   n 3)  ∆n uqr     n w qr      .

 n n  .  2) F  (1):   t  n   n,  

Proo. — 1) L 1.143)  w qr    n 

∇n t 

  n   ∇n t

3) B   w qr     D 1.102):          ∆n uqr     n w qr     ∆n uqr    qr   n uqr       n  qr ∆n  uq r  

   qr 

n  n

 qr 

   q   L 1.14 (2). T      n □ qr       n. 1.3.2. Applicaion o he Main Teorem. — L 1.143)     T 1.12  ta  tqn    t x  w qr   n     w qr  . L t x   w qr           L 1.15: { { }} ∑      r  a  x  tqn   i v i i   K ′ Cv i  n K  Q v S n n  ∑ ∑  n      q  r i hx i   q r i hai   r Cqr  

    n  Cqr                     q. T   . □ i 

i 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

36

2. From the Fundamental Formula to the Main Teorem 2.1. Interlude on the index. — L K      . 2.1.1. Index. — L n        P  P n     n       K. F  i       n  i  P  P      i . L z  z       zn    K  P  b  b      bn    n    . F  i       n  ti      zi  P K. Deinition 2.1. — L f  OPz       P       z. T  f     ∑ f  f ℓ t ℓ    tnℓn  ℓ ℓ  ℓn  Nn

 f ℓ  K. T index o f a z wih respec o he weigh b  { } b f  z   b ℓ      bn ℓn  f ℓ ,  

I f  ,  b  z  .

I b  b      bn    n    ,  n b      bn    b         b  b . T          s     L  P     z:  f      s   L  z   b s z  b ss   z 2.1.2. Higher dimensional Dyson’s Lemma. — T        H D D’ L:        N [50]. T    EV [28] (      )    . L r  r       r n    n   . C         P:

OP r    OP r        n OP r n  heorem 2.2 (H  D’ L). — Le z       z q  be K-poins o P and t       t q  be non-negaive real numbers. Suppose ha ▷ i z    , i z    or every i       n and every  ,  ; ▷ here exiss a non-zero global secion f  P OP r  such ha, or every        q, r f  z     t   

Ten he ollowing inequaliy is saised: q ∑

 

 ∆n t       qr  where qr 

MÉMOIRES DE LA SMF 152

n  ∏ i 

  

i  j n

{r } j

ri

 q     

2. FROM HE FUNDAMENAL FORMULA O HE MAIN HEOREM

37

2.1.3. Index a a single poin. — L z  z       zn    K  P, t        r  r       r n   n   . Deinition 2.3. — L Z qr z t     P         f   r f  z  t. C      P OP r :   Kr z t  K P OP r   Z r z t OP r  } {  f  P OP r   r f  z  t 

Proposition 2.4. — Keeping he noaion inroduced above, or every i       n le Ti  Ti  be a basis o K  such ha Ti  vanishes a zi . n r i ℓi ℓi 1) Te monomials Tz ℓ  Ti  or ℓ  ∇rZ t orm a basis o he K-vecor i  Ti  space Kr z t. 2) K Kr z t  #∇rZ t and 

 

K K  r z t   ∇n t  n r     r n 

K Z  r z t OP r    ∆n t    n r     r n 

3) K Z r z t OP r   #∆rZ t and  Proo. — L       .



2.1.4. Index a muliple poins. — L r  r       r n    n      t          N      .  

 

 

F        q  z    z       zn    K  P. S zi   ,    i       n.

 

, zi



Deinition 2.5. — C  q z  z       z q  . C     P, q  Z r z    t Z qr z t   

C      P OP r :

Kqr z t  KP OP r   Z qr z t OP r  { }  f  P OP r   r f  z     t          q 

R  uqr t     q      n    { { } }  ∆n uqr t      qr  q  ∆n t    

Proposition 2.6. — Keeping he noaion inroduced above: q  1) Z qr z t OP r   Z r z    t OP r .  

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

38

2) K Kqr z t  (2.1)

n ∏ i 

r i    q #∆rZ t. In paricular,

   

K Kq r z t    q  ∆n t  n r     r n 

3) Suppose uqr t  n. Le z   P K be a poin such ha or i       n and        q, one has i z   , i z   . Ten, or t   uqr t, Kqr z t  Kr z   t    

4)    

K Kq r z t   ∆n uqr t  n r     r n 

R  (3)  (4)  q   H D D’ L. Proo. — 1) T      Z r z    t’    ( [28, L 2.8]). 2) U    Kqr z t  KP OP r   Z qr z t OP r ,      K Kqr z t  K P OP r   K Z qr z t OP r   K P OP r  

q ∑

K Z r z    t OP r  

 

    q   P 2.43).

n ∏ i 

r i    q#∆rZ t

3) B         f    Kqr z t  Kr z   t  . T H D D’ L  q ∑

 

 ∆n t   ∆n t      qr 

   ∆n t    ∆n uqr t. T  t   uqr t     t   uqr t. 

4) I  ∆n uqr t  ,   uqr t  n,    . A uqr t  n. A  3),  t   uqr t, Kqr z t  Kr z   t    

T G’    

K Kqr z t  K P OP r   K Kr z   t    K P OP r   #∇rZ t  

   P 2.42)    q. T        q      r    t    uqr t. □ 2.2. Defnition o the “moduli problem”. — L K       VK     .

MÉMOIRES DE LA SMF 152

2. FROM HE FUNDAMENAL FORMULA O HE MAIN HEOREM

39

2.2.1. Linear acions on grassmannians. — L E    oK    . F    N  GN  E        N  E, i.e.  oK         GN  E  oK     {   O  F } X  f  X  S oK    f  E   N   

S   oK   G     oK  E. T,    N  ,  oK   G     GN  E      N ,     P N E    q       ON E. T P    GN  E  P N E  Gq.

2.2.2. Back o he Main Eecive Lower Bound. — L K ′      K   q  . L n      . L P  PoK n     n       oK . L r  r       r n    n      OP r        P,

OP r    OP r        n OP r n 

F  i       n  x i   K  PoK   ai   K ′  PoK   Kai   K ′. C    x  x       x n , a  a       an   P     a  a      HK  K ′ Q  L t x  t a           K    Kr x t x   f  PK  OP r   r f  x  t x    Kqr a ta   f  PK  OP r   r f  a  t a 

 PK      P. 3 S f  K  a  ,    a           a. D kr t x   kqr t a       K  Kr x t x   Kqr a ta . I   ,        PK  OP r     K  :   Kr x t x   Gkr tx  P OP r     Kqr a ta   Gkq r ta  P OP r   3. H      f ,     K ,    a,     K ′ ,        f  K ′ . A,     Q    K q r a t a   f  P OP r  oK Q  r f  a     t a     K ′  Q        G ,      K   Kq r a t a . I  ,  Kq r a t a  K Q  K r a   t a  

  K ′ Q

  K r a   t a   f  P OP r  oK Q  r f  a     t a .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

40

 n T oK   SLnoK     P  PoK        . W

Fr t x  

k∧ r t x 

   P OP r  

Fqr ta  

kq∧ r t a 

   P OP r  

   P ,   q        SLnoK :     Gkr tx  P OP r   P Fr t x       Gkq r ta  P OP r   P Fqr t a   2.2.3. Te geomeric invarian heory daa. — W    F F    :   Pr  Kr x t x  Kqr a ta      Xr  Gkr tx  P OP r  oK Gk t  P OP r   q r

a

G  SLnoK  Lr    Xr    P    

   :       jr  Xr  P Fr t x  oK P Fqr t a   P Fr t x  oK Fqr t a  

(T     P    G       S .) F     K  C    

Fr t x   C  Fqr ta   C 

k∧ r t x 

n ⊗

kq∧ r t a 

i 

 Sr i C 

n ⊗ i 

 Sr i C 

  q     ∥∥ Fr tx   ∥∥ Fq r ta      ( § 3   9). E     Fr t x  C Fqr t a         . T          SUn . D Lr        Xr . 2.3. Proo o the Main Teorem 2.3.1. — I   T 1.12       (T  2.7)      5.2     ( P  3.1, 3.2  4.1)    3  4.   T 1.12,    ,  n r  r       r n          . E , r      f   M E L B    r .

MÉMOIRES DE LA SMF 152

2. FROM HE FUNDAMENAL FORMULA O HE MAIN HEOREM

41

2.3.2. Semi-sabiliy condiions. —   T 1.12    F F     Pr ,      Pr  . I S 5.2    : heorem 2.7. — Le n   be a posiive ineger and r  r       r n  be a n-uple o posiive inegers. Le t x  t a   be real numbers wih t a  tqn . I he inequaliy    n uqr t a    n t x   qr 

is saised hen here exiss a posiive ineger      q n r  t a  t x  such ha, or every ineger     , he K-poin P  r  X r K is semi-sable under he acion o SLn wih respec o he polarizaion given by he Plücker embeddings. 2.3.3. Applying he Fundamenal Formula. — T             (SS)  T 1.12. T   T 2.7           q n r  t a  t x   ,        ,  K   P  r  K  r x t x  Kq r a ta 

 . T F F (, , C 1.7  C 1)           P  r    q: h L r P  r  

∑    v P  r   h   X r  L r  G  K  Q v S

        . D       n  r     r n       , (2.1)



∑ v P  r     n  K  Q v S    r     r n      

h L r P  r  n   r     r n 

    

  h   X r  L r  G  n  r     r n 



I          q   . T           Pr         x i ’  ai ’. I                    S’ L. H      q     A . T                       . I                 . T        q         .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

42

2.3.4. Upper bound o he heigh. — T P         Xr  P Fqr t a   P Fr t x . T:     Kqr a ta   h Lr Pr   h Fr tx  Kr x t x   h Fq r t a 

S    A  ( P 3.13.2) : n   ∑ h Fr tx  Kr x t x  

h



Fq r t a 



ℓi hx i 

i  ℓ ∇rZ t x 

n n  ∑    ∏ Kqr a ta   r i    kqr t a  q r i hai   r   q  i 

i 

A         r : (2.2)

   

h L r P  r   n  r     r n 





∇n t x 

  

n ∑

r i hx i 

i 

n  ∑    q  ∆n t a  q r i hai   r   q  i 

2.3.5. Upper bound o he insabiliy measure. — L v     K. I   v  :  { }   r k t t   a  x  v Pr    qr a a i v i i ′ i  n

  K Cv



n  ∑ i 



ℓ ∇rZ t x 

 kr t x   kqr t a     ℓi  r i v ai  x i   

              kqr t a 

n ∑ i 

   r i    kqr t a r     kr t x r   

          . T     S 4 ( P 4.1). I v  ,           f ,   P 2.6 2), 2.42)  2.64): { v P  r      q  ∆n t a t a  r i v ai  x i       n  i  n r     r n    K ′ Cv    n }  n t x    ∆n uqr t a  ∑    r i v ai  x i    i   I v  ,   r  ∆n uqr t a      ∇n t x            . B D 1.102),      n uqr t a    ∆n uqr t a   MÉMOIRES DE LA SMF 152

2. FROM HE FUNDAMENAL FORMULA O HE MAIN HEOREM

43

  (SS)   n t x    ∆n uqr t a   . B       v ai  x i   ∑ w ai  x i  w v

       w  K ′  v.        S     P 1.2, ∑ ∑ ∑∑   w ai  x i   w ai  x i   K ′  Q hx  hai   v S w VK ′

v S w v

   

     (2.3)

∑ v P  r   ,   n  K  Q v S    r     r n 

{ } ∑      r  a  x    q  ∆n t a t a i v i i   K ′ Cv i  n K  Q v S 

n  n t x    ∆n uqr t a  ∑ r i qhx i   hai   i      r   ∆n uqr t a      ∇n t x    

2.3.6. Lower bound o he heigh on he quoien. — F i       n  Ei  oK  bi  r i kqr t a   kr t x . A      T 2.1  C 1      G  SL E  oK    oK SL En   GL Fqr ta   Fr t x       

n ⊗ i 

Eibi 

n   r i kq r ta kr tx  ⊗ oK  Fqr t a   Fr t x  i 

T    Ei  ,     Ei     i       n. T   Gq  jr  Xr  P Fqr t a   Fr t x  T 2.1      h   Xr  Lr  G  h  P Fqr t a   Fr t x  O G        kqr t a   kr t x  r       kqr t a    kr t x  

      kqr t a    kr t x                 q        ( § 3   9). T  S’ ,  kqr t a       n  r     r n  

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

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44

   kr t x . T  ,       r , : (2.4)

    

   h   X r  L r  G   ∆n uqr t a    ∇n t x  r    n   r     r n 

Remark 2.8. — T    T 2.1  C 1   T 1.11  C 4,      h   Xr  Lr  G     kqr t a    kr t x  

,

    

h   X r  L r  G    n  r     r n 

      M T  f       (2.1)     q (2.2), (2.3)  (2.4). 3. Upper bound o the height 3.1. Rational point Proposition 3.1. — Wih he noaion inroduced in Secion , n ∑  ∑  ℓi hx i  h Fr tx  Kr x t x   i  ℓ ∇nZ rt x 

Proo. — L T T      K  . F  i       n  x i   x i    K        x i  P K. S  x i   . F  n    ℓ  ⃞ r  n ⊗ T ℓ  Tr i ℓi Txℓii i 

 Tx i  x i T  x i T . A    K  Kr x t x       T ℓ  ℓ   ∇rZ t x . L v     K. T H q (1)   10    ∧ ∑    T ℓ  ∥T ℓ∥P OP r v    Fr t x v

ℓ ∇rZ tx 

ℓ ∇rZ t x 

F  n    ℓ  ⃞ r          n   ∑    T ℓ   ∥Tr i ℓi Txℓii ∥v P OP r v

i 



n ∑ i 

r i  ℓi   ∥T ∥v 

n ∑ i 

C         .

MÉMOIRES DE LA SMF 152

ℓi  ∥Tx i ∥v 

n ∑ i 

ℓi  ∥x i ∥v 



3. UPPER BOUND OF HE HEIGH

45

3.2. arget points Proposition 3.2. — Wih he noaion inroduced in Secion ,

n n  ∑     ∏ h Fq r ta  Kqr a ta   r i    kqr t a  q r i hai   r   q  i 

i 

T             . 3.2.1. — Eq  oK  P OP r           n  ⊗    Sr i oK   P OP r   i 

D  P OP r    oK   . T oK    P OP r         P OP r      T ℓ 

n ⊗ i 

Tr i ℓi Tℓi

    . A,    v,          n n ∑ ∑   r i  ℓi   ∥T ∥ v  ℓi  ∥T ∥ v    T ℓ P OP r v  i 

I , (3.1)

i 

∑ ∑       P OP r     T ℓ P OP r v   v VK

ℓ ⃞

Z r

3.2.2. — E  K  Kqr a ta      oK         P OP r . T oK    Kqr a ta    P OP r   Kqr a ta 

 q         P OP r ,    C   P OP r  Kqr a ta 

    q    P OP r   C. D  C  oK        . W      (3.1):    Kqr a ta  K  Qh Fq r ta  Kqr a ta        C     P OP r     C  

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

46

3.2.3. — D  E  K  Z qr a ta  OP r    Ω   G   K ′  K. E  Ω  E K Ω     oΩ     . A  P 2.6: q  (3.2) E   E K Ω   

,     K ′  Q, E    Z r a    t a  OPΩ r  4 .       F i       n  ai   ai    Ω      ai  P K. S a         K  ai      ,   , ai   . F     K ′  Q,     Ω  E      n ⊗ Tr i ℓi T ℓi   Ta   ℓ  i 

ai

 

 Ta    T ai  T  ℓ  ℓ      ℓn       ∆rZ t a . L E   i

 oΩ    E       T ℓ’. Eq         T ℓ’    . D  E    oΩ   . F,   (3.2),  K  E K Ω     oΩ             oΩ    E  ’. D  EΩ     . 3.2.4. — T     PK  OP r   E  Z qr a ta  OP r        C oK K  E. A   q (P ‘S q’   11),    ∑  C    C   ∥ ∥ v      EΩ   (3.3) h Fq r ta  Kqr a ta   K  Q Ω  Q v V Ω

,    v  VΩ , ∥ ∥ v   v    , ∥ ∥ v 

 ,f  C Ω

∥f ∥ Ev  ∥ f ∥ Cv

T      ∥∥ v  . T oΩ    E        EΩ   .

3.2.5. — I     v      . F          q      PΩ  OP r   E           E K Ω  E   . D  ∥   ∥ v        . W  : ▷  v : ∥∥ v   ∥   ∥ v ;   q { }  ▷  v : ∥∥ v  q  ∥   ∥ v .   q

4. H   a       Ω  PΩ  PK K Ω  Z r a   t a      PΩ   t a    a   .

MÉMOIRES DE LA SMF 152

3. UPPER BOUND OF HE HEIGH

 

F        q  i       n  ϕ i   ϕi





47

     Ω  

 T  T    T   Ta     T   a i  T   i

 

C    ϕ r 

 

 Sr  ϕ 

 

     Sr n ϕ n

  Ω

PK  OP r  K Ω  Sr  Ω  Ω    Ω Sr n Ω   

   i       n    ϕ i     i       .   W        ◦ϕ r  PΩ  OP r   E            Z r    t a : T ℓ 

n ⊗ i 

Tr i ℓi Tℓi 



Ta   ℓ  ℓ  ∆rZ t a  



B    Ta   ℓ’        oΩ      E  . T   ∥   ◦ ϕ r ∥ v     

∥   ∥ v  ∥ϕ r  ∥ v  B         oK    V              V  V, n ∑           r i  ϕ i   Eo v  ∥ϕ r  ∥ v   ϕ r   EP OP r v  K

i 

T         . B           ϕ i   ϕ i  T      ϕ i  T   ai   . T, ▷  v  :            ϕ i   Eo v    ∥ϕ i  T ∥v  ∥ϕ i  T ∥v Ω         ai   ai   v 

▷   v :

             ϕ i   Eo v   ϕ i  T v  ϕ i  T v Ω          ai   ai   v   

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        K: n {∑ ∑ ∑        }  ∥∥ v   r i  ai   ai   v  r Ω  Q  q ′ v VΩ   K Q

v VΩ







i 

n ∑

v VΩ   K ′ Q i 

 Ω  Q

 ∑

       r i  ai   ai   v  r Ω  Q  q

n ∑

  K ′ Q i 

    r i hai   r   q 

 

D  Ω  Q,  hai   hai     K ′  Q    (3.3), n  ∑     r i hai   r   q  h Fq r ta  Kqr a ta    C q i 

U  C   P OP r    Kqr a ta    P OP r  

n ∏

r i  

 Kqr a ta   kqr t a 

i 

   .



4. Upper bound o the instability measure 4.1. Notations and frst reductions. — L v     K. Proposition 4.1. — Wih he noaion inroduced in Secion 2.2, i he place v is nonarchimedean,  { }   r k t t   a  x  v Pr     qr a a i v i i ′ i  n

  K Cv



n  ∑ i 



ℓ ∇rZ t x 

 kr t x   kqr t a     ℓi  r i v ai  x i   

whereas, in he v archimedean case, he previous inequaliy holds wih kqr t a 

n ∑ i 

   r i    kqr t a r     kr t x r   

added on he righ-hand side.

T     i       n    K ′  Cv :

1)   x i   x i    Kv  x i  P Kv    ∥x i   x i  ∥ v  .           2)   ai   ai    Cv  ai  P Cv    ∥ai   ai  ∥ v  ;       3)  q   i  Cv  ai  x i   ai  x i   .

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49

4.1.1. Elemens o SL measuring disances  

Deinition 4.2. — F i       n         q  дi      Cv    : ( )  (     ) ⊤   x i  x i     ai  ai     дi       GL Cv    xi  xi  a x i   a x i  ai  ai  i

C  n д

 



    д      дn 

i

 GL Cv n .

Proposition 4.3. — Wih he noaion inroduced above, or all i       n and        q,  

1)  дi

 

 

 ai  x i   ai  x i   ;  

2)    дi

 

v  v ai  x i ;

3) For a non-zero vecor y  y   Cv such ha ∥y  y ∥ v  ,

      v ai  y v x i  y v       д  yT  yT    i v      v ai   y  v x i  y v  

where T T denoes he canonical basis o Cv and y  P Cv  he line generaed by y  y .  

 

Proo. — 1) C:   x i   x i    ai   ai      . 2) C  1).  

3) T  дi  Cv       Cv     ,   (      T , T )  (     ) ai  ai   xi  xi 

T     .



4.1.2. Proo o Proposiion 4.1. — I   P 4.1    P  4.6  4.7:        . Deinition 4.4. — F h  h       hn   GL Cv n  ∥h  w x ∥ Fr tx v  , ▷ v h Kr x t x    ∥w x ∥ Fr tx v ∥h  w a ∥ Fq r ta v  , ▷ v h Kqr a ta    ∥w a ∥ Fq r ta v  w x  Fr t x   K (. w a  Fqr t a   K)      P     Kr x t x  (. Kqr a ta ). Deinition 4.5. — F i       n    K ′  Cv               дi  дi  i ,     . S д     д      дn .

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E      v Pr      {  } v Pr    n v h Kr x t x   v h Kqr a ta  h SL Cv  {  }        д  K x t     д  K a t    v r x v qr a ′   K Cv

T  Fr t x   Fr t a   GLnoK       

kr t x r  kr t a r . B P 4.32),   i

 

   v ai  x i   n   kr t x  ∑   д   Kr x t x   v д   Kr x t x   r i v ai  x i  v   i 

n   kqr t a  ∑   v  д   Kqr a ta   v д    Kqr a ta   r i v ai  x i   i 

O     P 4.1   :

Proposition 4.6. — Wih he noaion inroduced above, i v is non-archimedean, n ∑ ∑     v д   Kr x t x    ℓi v ai  x i  i  ℓ ∇rZ t x 

whereas, i v is archimedean, he preceding inequaliy holds wih kr t x r    be added on he righ-hand side. Proposition 4.7. — Wih he noaion inroduced above, i v is non-archimedean, { }   v д   Kqr a ta   kqr t a t a  r i v ai  x i   i  n

whereas, i v is archimedean, he preceding inequaliy holds wih n  kqr t a  ∑ r i    kqr t a r     i  added on he righ-hand side.

4.2. aylor expansion at the single point: proo o Proposition 4.6. — K      S 4.1. 4.2.1. — L i       n     

Ti   x i T  x i T  Kv 

S   x i   x i    Kv        Ti     . I v     Ti   ov       Ti  , Ti       ov  ov . I v    Ti   Kv       Ti  , Ti       Kv . S    Ti    x i   i       n, P 2.41)       K  Kr x t x       n ⊗ T ℓ  Tiri ℓi Tiℓi i 

MÉMOIRES DE LA SMF 152

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 ℓ  ℓ      ℓn    ∇rZ t x . T    Fr t x  oK Kv , ∧ w  T ℓ ℓ ∇rZ t x 

      P   Kr x t x . I v     T ℓ’      ov      Kr x t x   Kv  P OP r   ov 

T

 ∥w ∥ Fr tx v  

I v     T ℓ’            ∥w ∥ Fr tx v 



ℓ ∇rZ t x 

 ∥T ℓ∥P OP r v  

  r B   ℓi  r i , i

   r  ℓi   i  ℓ ∇rZ t x  i    kr t x r   

 ∥w ∥ Fr tx v  

 



n ∑

 



n ∑

ℓ ∇rZ t x  i 



ℓ ∇rZ t x 

n ∑

  r  ℓi  i

r i  

i 

4.2.2. — F  ℓ  ∇rZ t          n ∑          д   T ℓP OP r v  r i  ℓi   ∥дi  Ti  ∥v  ℓi  ∥дi  Ti  ∥ v  i 

T   H q, ∑      д   T ℓP OP r v  д   w  Fr tx v  ℓ ∇rZ t x 





n ∑ 

ℓ ∇rZ t x  i 

     r i  ℓi   д   Ti   v  ℓi  д   Ti   v 

F i       n P 4.33)        v  ▷ дi  Ti   v    v ;  

▷ ∥дi

 

 Ti  ∥ v  v ai  x i .

S  v  :

n  ∑   ∑        v д   Kr x t x    д   w  Fr tx v   ℓi v ai  x i  i  ℓ ∇rZ t x 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

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I v  :      v д   Kr x t x    д   w  Fr tx v  kr t x r    n  ∑   ∑    ℓi v ai  x i  kr t x r     i  ℓ ∇rZ t x 

   .



4.3. aylor expansion at the algebraic points: proo o Proposition 4.7. — K     S 4.1. 4.3.1. — I v    ov     Kv   f       fkq r ta       ov :     Kqr a ta  K Kv  P OP r  oK ov 

I v    f       fkq r ta       Kqr a ta   Kv . W      Fqr a ta  oK Kv , w 

kq∧ r t a 

f

 

      P   Kqr a ta . I       ∥∥ v      Cv   P OP r oK Cv . W   H’ q (1)   10  kq∑ r t a              v д  Kqr a ta    д  w Fq r ta v   д   f   v   

      :

Lemma 4.8. — Le f be a non-zero elemen o Kqr a ta . Wih he noaion inroduced above, i v is non-archimedean, { } ∥д   f ∥ v    ta  r i  v ai  x i   i  n ∥ f ∥v

whereas, i v is archimedean, he preceding inequaliy holds wih  ∑ r i    r     i  n

added on he righ-hand side.

4.3.2. — F i       n    :  

 

 

 

Ti   ai  T  ai  T  Cv 

S   ai   ai    Cv        Ti     . I v    ov       Cv   Ti   ov     MÉMOIRES DE LA SMF 152

4. UPPER BOUND OF HE INSABILIY MEASURE

53

  Ti  , Ti       ov  ov . 5 I v    Ti   Cv       Ti  , Ti       Cv . F  n   ℓ  ℓ      ℓn   ⃞ r  n ⊗ T ℓ  Tiri ℓi Tiℓi  i 

T  T ℓ’      Cv   P OP r  K Cv . I v      T ℓ’      ov  P OP r  oK ov . I v     T ℓ’      ℓ  ⃞ r , n       ∏ ri ∥T ℓ∥ v  rℓ   ℓi i 

4.3.3. — I v  ,         4.2.2  n n ∑ ∑           ℓi  v ai  x i   ℓi v ai  x i   д   T ℓ v  i 

i 

 ,  v  ,   q   kqr t a r         .  4.3.4. — W f  ℓ f ℓT ℓ  f ℓ  Cv . I v  , } { ∥ f ∥ v    f ℓ v  ℓ  ⃞ rZ  I v  ,

∥ f ∥ v   



ℓ ⃞

Z r

    f ℓ v rℓ 

S    v ai  x i      ℓ  ∇rZ t a : n n { ∑      ∑     } ℓi   r i v ai  x i ℓi v ai  x i  r i  n i  i  i { }    ta  r i v ai  x i   i  n

B     f  r f  a     t a ,  , f ℓ     ℓ  ∆rZ t a . I     : {     }   f ℓ v   д   T ℓ v  д   f  v   ℓ ∇rZ t a 

 ta 

i  n

{     } r i v ai  x i   ∥ f ∥ v 

       .

 5. S  Ti     ov  ov Ti  ov  ,   (.[11, 1.6.1 P 2]). O        Ti        Kv . I       Ti          ,         .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

54

4.3.5. — S  v . P 4.33)    q : ∑       д  f    f ℓ v  д   T ℓ v v ℓ ∇rZ t a 

(4.1)

 

i  n

{

 

v ai  x i r i

} ta



ℓ ∇rZ t a 

 f ℓ v

n  ∏



r i ℓi



i 

C ℓ   ℓ    P OP r    J’ q: √ n  n n ∏  ∑ ∏ ∏ ∑ r i ℓi  f ℓ v   r i    f ℓ v r i ℓi  i 

ℓ ∇rZ t a 

    P OP r     f : ∑

ℓ ∇rZ t a 

 f ℓ v

n ∏ i 

i 

n

i  r i

r i ℓi  

   U ba  ba ba  b ,     .

i 

 . T       



ℓ ∇rZ t a



ℓ ∇rZ t a 

ℓ ∇rZ t a

n {  ∏ } r r i ℓi  ℓ  i 



ℓ ∇rZ t a 

n {  ∏ } r r i ℓi ∥ f ∥v   ℓ 

    f ℓ v rℓ

i 

n {  ∏ } r r i ℓi   r  A  (4.1)    ℓ ℓ ∇rZ t a  i  □

5. End o the proo: semi-stability in the general case 5.1. Basic acts about the semi-stability o subspaces 5.1.1. Insabiliy coefcien. — L K      G  K      K X q   Gq   L. L x   K  X . L   Gm  G      G (         )      x  Gm  X    x       x 

B   X ,    x    q     x  A  X . D  x   K x . S          Gm ,  Gm    K  x  L        L x 

  L  x  Z. I    insabiliy coefcien o x            L. 6 6. W       [48, D 2.2].

MÉMOIRES DE LA SMF 152

5. END OF HE PROOF: SEMISABILIY IN HE GENERAL CASE

55

heorem 5.1 (HM ). — Suppose ha K is perec and L is ample. Wih he noaion inroduced above, he poin x is semi-sable i and only i  L  x  

or every one-parameer subgroup   Gm  G.

T      M [48, T 2.1]  K   . T        K [45, T 4.2]  R [59]. 7 5.1.2. Insabiliy coefcien o linear subspaces. — L V     K   r    . C    r    Gr V    P    Gr V   P r V .

S   K  G    V . T       Gr V ,     P r V     q      r O  P V . S  P    Gq     ,       O  Gr V      Gq . Deinition 5.2. — L   Gm  G    . 1) L W  V       r . S       W      O  W       O.

2) F   p  Z      Vp  v  V     v   p v 

L p  (. p  )    (.  )  p   Vp   .  3) F   p  Z  V p  q p Vq .  S       ,   V  p Z Vp . I ,    p  p   V p  V  p  p  

Proposition 5.3. — Le W  V be a linear subspace o dimension r . Se W p  W  V p or every ineger p. 1) Te subspaces W p orm a decreasing lraion o W and   ∑     W   p K W p  K W p   p Z

 p  K W 

p∑  

K W p

p p   

7. I     [45, T 4.2]   T 5.1         K’  M’       [48, A  C 2,  B].

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

56

  2) Le w       w r be a basis o W . For every i       r le   w i  be he insabiliy coefcien o he poin w i   PV . Ten he vecor w i wries as      w i     w i  w i         wih w i  V . I he elemens w       w r  V are linearly independen, hen r     ∑   w i     W   i 

3) Wih he noaions o (2), here exiss a basis w       w r o W such ha heir componens o minimal weigh w       w r  V are linearly independen.

Proo. — T        [48, C 4, §4]. S  [67, § 2, L 2]. □ Proposition 5.4. — Le W , W be subvecor spaces o V . Ten: 1) (I ) I W is conained in W , hen     (5.1)   W     W   p  K W  K W 

2) (G )         (5.2)   W     W     W  W     W  W  

Proo. — 1) C. 2) F   p   G          K W p  K W p  K W p  W p  K W p  W p 

C    W p  W p  W  W p.



Remark 5.5. — T      P       :  V       W  W    W  W    (         V ). I,        2) . 5.2. Asymptotic semi-stability: proo o Teorem 2.7

5.2.1. — G       S 2.2. T           [63, §2 L 2]. I         P  r          X r . F       K (  P      PK n ). heorem 5.6. — Le n   be a posiive ineger and r  r       r n  be a n-uple o posiive inegers. Le t x  t a   be real numbers wih t a  tqn . I he inequaliy    n uqr t a    n t x   qr 

is saised hen here exiss a posiive ineger      q n r  t a  t x  such ha, or every ineger     , he K-poin P  r  X r K is semi-sable under he acion o SLn wih respec o he polarizaion given by he Plücker embeddings.

MÉMOIRES DE LA SMF 152

5. END OF HE PROOF: SEMISABILIY IN HE GENERAL CASE

57

5.2.2. Compuaion o he insabiliy coefciens. — F  n    r  r       r n ,     t     i       n : ∑ Z t  ℓi  r i  ri ℓ ∇rZ t 

Z t  . A     L 1.11    ri

Deinition 5.7. — L   Gm  SLn K    . 1) F i       n,     Ti  Ti   K      m i    ,     Gm K,    Ti    m  i Ti  

   Ti    m  i Ti  

T n    m   m        m n     weigh o     Ti  Ti  ( i       n)    adaped basis or . T  m i          . I m i      Ti     Ti       . 2) W    ,   Q y  P     Ti    y  i y   . D  y   q K  P    i y       i       n     insabiliy poin o  (      ).

Proposition 5.8 (I f    ). — Le   Gm  SLn be a oneparameer subgroup. Wih he noaion inroduced above, or i       n, n   ∑ Z   Kr x t x      i x m i  ri t x  i 

Proposition 5.9 (I f    ). — Le  be a posiive real number. Under he assumpions o Teorem  here exis a posiive real number   and a posiive ineger   he wo o hem possibly depending on n, q, r , t a and t x  saisying he ollowing properies: or every one-parameer subgroup   Gm  SLn , every ineger     and every real number       , n    ∑  m i  Zri uqr t a      n r i r     r n qr       Kq r a ta   i 

Proo o Teorem 2.7. — A   HM  (T 5.1)                         Gm  SLn ,        P  r     K  r x t x     K  r a t a   

L      . L   ,        P 5.9. U            ,  i       n,            :

(SS ′)

 Zri uqr t a      Zri t x    n r i r     r n qr   

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

58

 F            . P 5.8  5.9     P  r    : n ∑ i 

] m i  Zri uqr t a      n r i r     r n qr        i x   Zri t x   

S   m i     ,      (SS ′). T   . □ Proo o Proposiion 5.8. — C   Ti  Ti    (i       n). S  i x    i       n (       ). U      i  K   Ti    i Ti    x i . A  P 2.41),     K  Kr x t x         n ⊗ Tiri ℓi Ti    i Ti  ℓi  T ℓ  i 

 ℓ  ℓ      ℓn   ∇r t x . T          n   ⊗  m  i r i ℓi  Tiri ℓi Ti    m  i  i Ti  ℓi i    T ℓ  i 

S   m i     ,    T ℓ          ni m i r i  ℓi ,   T ℓ 

n ⊗ i 

T  T ℓ  ℓ  

Tiri ℓi Tiℓi 

∇rZ t x    ,



  Kr x t x  

n ∑



i  ℓ ∇rZ t x 

m i ℓi  r i  

 P 5.32) 

n ∑ i 

Z m i  ri t x 

5.2.3. Proo o Proposiion 5.9 Lemma 5.10. — Le   Gm  SLn be a one-parameer subgroup. Suppose 8 uqr t a  ,  n Le a  be a K-raional poin o P . Ten, or   ,       Kqr a ta     Kr a   uqr t a    n  ∑  kqr t a   kr uqr t a      P OP r  m i r i  i 

Proo. — T  uqr t a  ,  n ,  D 1.104),    ∆n uqr t a     qr  q  ∆n t a 

8. I uq r t a    n  C (SS)  T 2.7      n    n n .

MÉMOIRES DE LA SMF 152



5. END OF HE PROOF: SEMISABILIY IN HE GENERAL CASE

59

S   a   K   i a   , i a      i       n     K ′  Q. A  P 2.63),   Kqr a ta   Kr a   uqr t a     

(   Q     K). G’    f (P 5.4 2)     Kqr a ta   Kr a   uqr t a    :       Kqr a ta     Kr a   uqr t a         Kqr a ta   Kr a   uqr t a    

W      5.1.2,    b       P OP r b     ni m i r i (      r      Tnr n ). T   (P 5.41)   T     Kqr a ta   Kr y uqr t a      P OP r    .



Lemma 5.11. — Le  be a posiive real number. Under he assumpion o Teorem 2.7 here exis a posiive real number   and a posiive ineger   he wo o hem possibly depending on n, d, r , ta and t x  such ha, or every ineger     and every real number       :    K P OP r     1)      n   r     r n   Z   #∇ r uqr t a       2)   q  ∆n t a   qr   ;   n r     r n  3)

kq r t a  n  r     r n 

      q  ∆n t a    

Proo. — 1) C. 2) F     uqr t a    3)   P 2.6 2). □ Proo o Proposiion 5.9. — L                L 5.11.                  . L a   PK   q     i a       i       n. A P 5.8    a  : n ∑     K  r a   uqr t a      m i  Zri uqr t a    i 

A  L 5.11  P 2.42):     kq r t a   k  r uqr t a       P OP r    n r     r n qr   

T L 5.10 : n    ∑  m i  Zri uqr t a      n r i r     r n qr       Kq r a ta   i 

   .



SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

60

6. Semi-stability on P  P and the Wronskian determinant

I              n        W . S qr  q  r   r  r   r   

W r   r       .

6.1. — T       : heorem 6.1. — Le r  r   r   be a couple o posiive inegers such ha r   r  . Le t x  t a   be non-negaive real numbers such ha       t x     q  ∆ t a       q  ∆ t a   q r 

I he inequaliy (6.1)

    q  ∆ t a   q r   

is saised hen here exiss a posiive ineger      q r  ta  t x  such ha, or every ineger     , he K-poin P  r  X r K is semi-sable under he acion o SL wih respec o he polarizaion given by he Plücker embeddings. I ,             ▷ t a  tq        q;

▷ t x     q   w           w        q r  

T      M E L B    n  . Proposition 6.2 (I f    ). — Le  be a posiive real number. Under he assumpions o Teorem 6.1 here exiss a posiive ineger   (possibly depending on q, r , ta and t x ) saisying he ollowing properies: or every one-parameer subgroup   Gm  SL K and every ineger     :       Kq r a ta    r r  ⟨m   r ⟩   q  ∆ t a             q  ∆ t a   q r  

where ⟨  ⟩ denoes he sandard scalar produc on R .

A       T 2.7    T 6.1  P 6.2. T       P 6.2   : Proposition 6.3. — Le f  Kr a ta  be a non-zero secion. I  q  ∆ t a  q r   , hen, or every one parameer subgroup   Gm  SL K ,        f   ⟨m   r ⟩      q  ∆ t a   q r  

he insabiliy coefcien o f being aken as a poin o PP OP r  and wih respec o he inverible shea O.

MÉMOIRES DE LA SMF 152

6. SEMISABILIY ON P  P AND HE WRONSKIAN DEERMINAN

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Proo o Proposiion 6.2. — L      . A     L 5.11                  :

kq r t a       q  ∆ t a      r r  L f       fkq  r ta      Kq r a ta         (   ) f       fkq  r ta     (       P 5.3). T P 5.32)  (6.2)

    Kq r a ta  

kq∑  r t a 

    f ℓ 

    kq r t a ⟨m   r ⟩      q  ∆ t a   q r   ℓ 

   q   P 6.3. C  (6.2).



T            D’ L: heorem 6.4 (c. C 6.15). — Le f  P Or  be a non-zero global secion and le b  b  b  be a couple o non-negaive real numbers. Le y be a Q-poin o P . Le q   be an ineger and or every        q le z   be a Q-poin o P. For every i    suppose: 1) i z    , i z    or every  ,  ; 2) i z    , i y or every        q. For every        q suppose t    and q ∑    (6.3)   ∆ r f  z     q r     

Ten, b f  y  bi r i  and ) ( q ∑   b f  y    ∆  ∆ r f  z     q r  bi r i   

A    D’ L          [28, . 489]. T  (6.3)  q    EV  b f  y   “ ” ( loc. ci.).

I    P 6.3      f        (      ): Proposition 6.5. — Le   Gm  SL K be a one parameer subgroup and x an adaped basis or . Ten, or every non-zero elemen f  P OP r ,     f   ⟨m   r ⟩   m  f  y   where y  is he insabiliy poin o  wih respec o he chosen adaped bases.

Proo o Proposiion 6.3. — I f   T 6.4    z    a      K ′  Q,   b  m     y  y  (    ):  t a   ( (6.1)   ),  ∆ t a    t a . □

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

62

T          T 6.4. I   P 6.5,                D’ L — i.e. T 2.2  n   9 —         . U,   D’ L               :          r    z           q    m     y  . T       T 6.4                   . A               : Proposition 6.6. — Le b  b  b  and c  c   c   be couples o non-negaive real numbers. Suppose ha is made o posiive real numbers. For all i    le fi  P  OP r i  be a non-zero secion. Ten, or all Q-poin z o P , b f   f   z  bi c i  c f   f   z

I  ,     T 6.4  W       . 6.2. Homogeneous Wronskian. — I            SL K . W      [1, 2.8]. L r           r  .

Deinition 6.7. — L f       f   Sr K    T T      K  . T homogeneous Wronskian    f       f  : ) ) ( ( r        f ℓ    Wf       f    j r T Tj j ℓ    I     S r   K  ,  ,      r     T T (        r    ).

T    [1, 2.9]         W. I   W’     [8, P 6.3.10]  f       f         Wf       f     . T W       Sr K             ∧ Sr K   S r   K   W 

9. T      D [27],          ( [7], [68]  [70]).

MÉMOIRES DE LA SMF 152

6. SEMISABILIY ON P  P AND HE WRONSKIAN DEERMINAN

63

Proposition 6.8 (. [1, 2.3, 2.5  2.8]). — Te ollowing properies are saised:  1) I T′T′ is a basis and W ′   Sr K   S r   K  is he Wronskian map aken wih respec o he later basis, hen as linear maps, W ′  T′T′  r   W

where T′T′  is he linear map sending Ti on Ti′ or i   . 2) Te linear map W is equivarian under he acion o SL K on he vecor spaces  Sr K  and S r   K  .

6.3. ensorial rank. — L V  V   K .

Deinition 6.9. — T ensorial rank     v  V K V          v       v  v      v  v   vi ℓ  Vi  i     ℓ       . D   v. T         GLV   GLV  ( ). T    v         V  V   v     V K V ≃ HK V  V 

(         V  V ). v  F i     vi       vi v   Vi    v  ℓ  v ℓ  v ℓ . T,  i   , vi       vi v    . 6.4. Splitting polynomials through the Wronskian. — L r  r   r           i     Vi  Sr i K  . W  ,    P OP r  ≃ V  V 

F   f  P OP r        f      . W    [7, . 266], s  f   f    F  i       Ti  , Ti   K  . Deinition 6.10. — L f  P OP r          f     . F      ℓ  ℓ  ℓ    ℓi    i   , :   f   , f  ℓ ℓ ℓ ℓ   ℓ   T  T T  T       OP r      r     . T homogeneous Wronskian Wf       [∏   r i       ]   Wf     ℓ f  ℓ ℓ    ri  i        OP r      r       .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

64

L f  P OP r          f     . W f 

 ∑

ℓ 

f ℓ  f ℓ

 fi ℓ  P  Or i    i      ℓ       . F i       W Wi f   Wfi       fi         Ti  Ti  . A   : Proposition 6.11. — Wih he noaions inroduced above, Wf   W f   W f  6.5. Index o the Wronskian. — I      W         . Proposition 6.12. — Le f  P OP r  be a non-zero secion and le b  b  b  be a couple o non-negaive real numbers. Ten, or every Q-poin z o P, ) (    f      ∆ t  f  r  b Wf  z  bi r i  f      r

where t   b f  z bi r i .

Proo. — S  W    (     )      (P 6.8),   i         Ti  , Ti   K    Ti  i z ,   Ti  i z  . L t  b f  z     f  z. L   f       f ,       r   r  . S     T  T       z,   ℓ  ℓ       ,   { }   b ℓ  ℓ  f  z    t  ⟨b ℓ   ℓ  ⟩   } { ℓ   bi r i    r bi r i     t  r   ⟨ ⟩ ⟨ ⟩ ℓ    b ℓ   ℓ    bi r i  r  ℓ   ℓ    bi r i   r   r

( r  r   r     ℓ        r  ). L S           . S     ,  {∑ }     b  ℓ  ℓ  f  z b Wf  z    S

 

 S

MÉMOIRES DE LA SMF 152

ℓ 

 {∑

{ }} ℓ   t  bi r i    r bi r i  r ℓ 

6. SEMISABILIY ON P  P AND HE WRONSKIAN DEERMINAN

W t ′  t bi r i   u    r   t ′ ,

F,

65

  ∑  ℓ ℓ  t′     t  bi r i   bi r i  r r ℓ  ℓ 

 ∑



r u

r u    ∑ ℓ u u  r u t ′   t′   r u   t ′  r   ℓ 

C :

Lemma 6.13. — Wih he noaions inroduced above, le t  t ′ . Ten,     u      ∆  t  u t′   r r Proo o Lemma 6.13. —      :

▷ S u  t ′. T, ut ′   u   t ′ ,      r  ,         r r

▷ S u    r  . T,   u u  u t   u t′    T    t    t                   t  . B , u  t,        u    r  , u t  u t    t  u  u t  t 

    q     q t  t   . T      . □ T      .



Proposition 6.14. — Le f  P OP r  be non-zero and b  b  b  a couple o nonnegaive real numbers. Le q   be an ineger and or every        q le z   be a Q-poin o P. For every i    suppose i z    , i z    or every  ,  . Ten, q ∑

 

where t

 





 ∆ t       q r 

  i        q   r f  z         b f  z  bi r i  i    SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

66

Proo. — S f   . T            b Wf  z  . ▷ Upper bound. – B    P 6.6. S Wf   W f   W f  P 6.6     c  r  b Wf  z    bi r i  r Wf  z   I    r Wf  z  . S   f . U     ,    Wi f      Or i      P          z     :  ∑     Wi f  i z   r i  i ) ( q  ∑ ∑      r i       Wi f  i z   r i  i  

r Wf  z   

q   ∑      ∑    r Wf  z    ri i   

F        q, P 6.12 (  z  z    b  r ) :

       ∆ t    r Wf  z         r { }  t      r f  z    . S ,   b Wf  z     ,  q r  q r ,    q     ∑     ∑   bi r i      q r        ∆ t   ri r i   

▷ Lower bound. – P 6.12     z  z      b :

 t 

       ∆ t   b Wf  y  bi r i      r { }    b f  z   bi r i  .

C         b f  z  :

q       ∑          q r   ∆ t        r r  

MÉMOIRES DE LA SMF 152

6. SEMISABILIY ON P  P AND HE WRONSKIAN DEERMINAN

(      r    ). D           r   : q ∑

 

67

 r 



          q r   r      q r     q r  

 ∆ t    

   f      ,           (        r  ) —  [7, L 2  II.4]   . T       f   . T        f   . □ Corollary 6.15. — Under he assumpions o Proposiion 6.14, suppose   r f  z     or        q and (6.1)



Ten, b f  z



q ∑

 

   ∆ r f  z     q r   

  bi r i  and

 ∆

q ∑   b f  z      ∆ r f  z     q r    bi r i   

Proo. — I b f  y  bi r i , P 6.14   

  (6.1).

 

q ∑

 

   ∆ r f  z     q r 



6.6. Wronskian as a covariant. — L      . F      . T W   “”     SL K , i.e.    SL K q      W  P P OP r  d P S r    K  K S r    K  

       U   PP OP r        f  P OP r      . T W  W    SL K q     W O ≃ O U  . I       ,              R’     G I T.      ,             O  f    O  Wf    SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

68

CHAPER 2. DIOPHANINE APPROXIMAION ON P VIA GI

    f  OP r             Gm  SL K . I y              , P 6.5        m  Wf  y    m  f  y       m    m    A  ,     T 6.4    y  y     b  m  . U,               Pr (   t x   ). I          P 6.12     P 6.14.

MÉMOIRES DE LA SMF 152

CHAPER 3 KEMPF-NESS HEORY IN NON-ARCHIMEDEAN GEOMERY

I               K  N [46]         ( )      . E            ,  q                   . T           ,          . I S 1       K  N                     . T                       C 4. I S 2              :   (   B    ),      . C               ,              . C      ,       . W                       (    B   T’        ). S 3      :                      ( T  3.3). T           GI q (      ,  T 1.6). T                ,    ,   B   .

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

70

I                 GI q. W                  ,      B  . T       C 4. 1. Statement o the main results 1.1. A result o Kemp and Ness. — L G    ()     V   ( )   G      ∥∥  V  R . S     ∥∥            U  G. L v     V . K  N      [46]       pv  G  R   pv д  ∥д  v ∥  

A    ,        : heorem 1.1. — Wih he noaions inroduced above: 1) Te uncion pv obains is minimum value i and only i he orbi o v is closed. 2) Any criical poin o pv is a poin where pv obains is minimum. 3) I pv obains is minimum value, hen he se where pv obains his value consiss o a single U - Gv cose here Gv is he sabiliser o v in G. 1.2. Interpretation via the moment map. — A   GS  M,       G I T  Kä          . I         PV   L U     G  V    . F    v  V ,        a  L U  1

 v   L U  R

 ⟨a v v⟩   i ∥v ∥  H ⟨  ⟩         ∥∥, i   q       L U V  V    .  v  a 

S  v  V   2  pv д  pv e   д  G    PV            . Proposition 1.2. — A non-zero vecor v  V is minimal i and only i he linear map  v  is idenically zero. (F          [48, T 8.3].) 1. O             . 2. T                G  v    v .

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE MAIN RESULS

71

W    2)  T 1.1     q:     PV   M     PV      PV     G  O. L Y   q  PV   G. T      U  Y C

   [48, T 8.3]. W    U  ,  q    U    MW    q. T          GS [40], [41], [42],       K [48, C 8]  W [72]. 1.3. Present setting. — I         : ▷   C    k       ; ▷    V   kf  X        k  G; ▷   ∥∥     u  X     ( D 2.29)       U  G ( D 2.20  2.21). AL [3]     X     f  (      S )  u  X C  R   U       . S 1)  3)  T 1.1             : Example 1.3. — C       C  C   t  x y  tx y

T ℓ   ∥x y∥  x  y             U. H              t   t  C ,      t       



  t  C . T      “”         . M      t   t     “”           U.

I             KN    ,            G I T. 1.4. Algebraic setting. — L k   . L G    k    f k X  S A   . D  Y        AG     X  Y       AG  A.

T    G I T   f       ( [48, T 1.1  C 1.2]   , [43]     [63, T 3]    ).

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

72

heorem 1.4. — Te k-scheme Y is o nie ype and he morphism  saises he ollowing properies: 1)  is surjecive and G-invarian; 2) le K be a eld exension o k and  K  X K  X k K  YK  Y k K be he morphism obained exending scalars o K; hen or all poins x x ′  X K,  K x   K x ′

i and only i G K  x  G K  x ′ , ∅

he orbis being aken in X K . 3) or every G-sable closed subse F  X is image  F   Y is closed; 4) he srucural morphism  ♯  OY    OX induces an isomorphism   ♯  OY    OX G 

I  Y    q  X  G     k, i.e.  G   ′  X  Y ′    q   Y . F  ,       Y    quoien  X  G    quoien morphism   projecion (on he quoien). 1.5. Analytic setting. — S     k            . K       G  (. X  , . Y  )  k       kf  G (. X , . Y ). H,       q         ;          B. W            S 2.1:          . T k  G     k  X      k    X   Y       (   )    G  . L   G k X  X     k     G  X . Deinition 1.5. — T orbi    x  X      X    G   x     x

A  F  X      G  -sable (. G  -sauraed)     x  F ,   G   x (.   G   x   )    F . I         . I  ,    x y  X  , y  G   x  x  G   y

(          x  y       ;  [5, P 5.1.1]).

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE MAIN RESULS

73

1.6. Analytic topology o the GI quotient. — O         1)–3)  T 1.4     k : heorem 1.6 (c. P 3.1  3.9). — Wih he noaion inroduced above, he morphism    X   Y  saises he ollowing properies: 1)   is surjecive and G  -invarian; 2) or every x x ′  X  :   x    x ′

i and only i G   x  G   x ′ , ∅

3) i F is a G  -sable closed subse o X  , hen is projecion   F  is a closed subse o Y  . I     1)  2)     “”  (T  1.4 1)–2)). I   2),        G  x    x  X C      X :            Z . T       q     K  N. A       N [51]. T 1.6       q,       : Corollary 1.7. — Wih he noaion inroduced above, he ollowing properies are saised: 1) or every poin x  X  here exiss a unique closed orbi conained in G   x; 2) or every G  -sauraed subses F  F ′  X  :   F     F ′ , ∅

i and only i

F  F ′ , ∅

3) a subse V  Y  is open i and only    V   X  is open; 4) le U be an open subse o X  ; hen U is G  -sauraed i and only i U       U  i U saises one o his wo equivalen properies, hen is projecion   U  is an open subse o Y  . I     Y        q        3  X    q : x RG x ′  G   x  G   x ′ 

I   ,    ♯  OY    OX G           ,  ,    , 

 ♯  OY    OX G 

  . T       q  S  (   [62, C 5, P 43)])      L’ S T (  ,        ). N,           —     S      ,      3. A   S          S  .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

74

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

     (  )  R        . Qestion. — I   ,     , 

 ?

 ♯  OY    OX G 

1.7. A variant o the result o Kemp-Ness Deinition 1.8. — A  u  X         invarian       G        U  G     :    t  G  k X     t  U,     u   t  u  t 

   G k X  X        G  X .

heorem 1.9 (c. T 3.3). — Le u  X     be a plurisubharmonic uncion which is invarian under he acion o a maximal compac subgroup o G. For every x  X  , 

  x ′   x 

ux ′ 



x ′ G  x

ux ′

Deinition 1.10. — L u  X       . A  x  X     : ▷ u-minimal on  -bre  ux  ux ′   x ′  X     x   x ′; ▷ u-minimal on G-orbi  ux  ux ′   x ′  G   x. T   u     (. u   G)    X  u (. X G u). Corollary 1.11 (c. C 3.4). — Le u  X     be a plurisubharmonic uncion which is invarian under he acion o a maximal compac subgroup o G. Ten, 1) a poin x is u-minimal on  -bre i and only i i is u-minimal on G-orbi; 2) X  u  X G u; 3) i u is moreover coninuous, he se o u-minimal poins on  -bres X  u is closed. I           K  N    q  T 1.9: Corollary 1.12. — Wih he noaion inroduced above, le u be opologically proper. Le x  X  be a u-minimal poin on is G-orbi (hus on is  -bre). Ten here exiss a poin x   G   x such ha is orbi is closed and ux    ux. Proo. — I  x ′  G   x       . I f     □  x      x ′ (   u   ). T q    T 1.9          U               K  N. T     S 3.5.

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE MAIN RESULS

75

1.8. Metric on GI quotients. — L X    k        G. L L   G   . S  L       ∥∥L :    ,      U  X     s  U  L  ,    ∥s ∥LU  U  R       x  U : ▷ ∥s ∥LU x       sx  ; ▷ ∥s ∥LU x  ∥s ∥LU x     k; ▷     V  U , ∥s ∥LV  ∥s ∥LU V . N                   L. L X          X    Y    q  X   G. L   X   Y   q . F  D           M D  Y      , ϕ D    M D  L D  X       G ( [48, T 1.10]). D     M D  :  y  Y     t  M D       y,  ∥t ∥M D y   ∥ t ∥L D x  x y

O       , i.e.       ( P  4.5). heorem 1.13 ([75, T 4.10], c. T 4.6  C 3). — Make he ollowing assumpion: ▷ he meric ∥∥L is invarian under he acion o a maximal compac subgroup o G; ▷ or every analyic open subse U  X  and every secion s  U  L   ha does no vanish on U , he uncion   ∥s ∥L  U  R is plurisubharmonic. Ten, he meric ∥∥M D is coninuous. Remark 1.14. — I   ,    ∥∥ L      FS         KN. Z               FS                     ( [73, T 2.2]  [15, A A]). T        Kä     ∥∥ MD    [74, T 2.2]. Remark 1.15. — I   ,                 . M ,  X    k ◦         k ◦  G. S  X  q   G    L. L X , G  L       X, G  L. T          L      ∥∥ L ( § 4.1.3). T,    ∥∥ L            G   G ( D 2.21) ,

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

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 L  ,     ∥s ∥ L         U  X      s  U  L   ( C 4.4).

heorem 1.16 (c. T 4.6). — Under he assumpions o Teorem 1.13 suppose ha k is non-rivially valued and algebraically closed. Le x  X  k be a semi-sable k-poin o X and t   x MD be a non-zero secion. Ten, 

 x ′  x 

∥ t ∥L D x ′   ∥ t ∥L D д  x д G k 

where he supremum on he le-hand side is ranging on k-poins x ′ in he bre o  x. S  k       Qp     F t    F . W    R 1.15  X         X  Y   q  X . F  D           MD  Y        X ,   ϕ D    MD  LD X L ∥∥ MD         MD .

heorem 1.17 (c. T 4.11). — Le k be eiher a nie exension o Qp or o he orm F t or a eld F and le K be he compleion o an algebraic closure o k. Le y be a K-poin o Y and le t  y  M D be a secion. Ten, ∥t ∥ MD y   ∥ t ∥ LD x  x y

where he supremum on he righ-hand side is ranging on K-poins x o X in he bre o y. 2. Preliminaries to the local part L k             k . 2.1. Analytic spaces 2.1.1. Overview. — O         k. T   : 4 1) T  :  C           . 2) T  :  R     R      q X   X         X  X    . 5 4. T  R  C            . 5. N  q X    R    X   OX     : ▷    X     q X     q ;

▷    X  X      ,     U  X           OX     U  OX      U  OX   f  U  OX    ♯ f   f    ♯  OX    OX        R     .

MÉMOIRES DE LA SMF 152

2. PRELIMINARIES O HE LOCAL PAR

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3) T  :    k          ( ) k      B  . R          B [5], [6];        [57, §1.2],             B’    [23]. W         k. I     ,            k  X  B [5, §1.5, §3.4  §3.5], P [54], N [52, §2],      . 2.1.2. Underlying opological space. — L X   k   . Deinition 2.1. — T   X      X     x        x  X (  )          x  R      k       k ( x      x). T  X          ,     U  X, 1)   U    x     X    x  U     X  ; 2)    f  U  OX ,           f   U    R   f   x      f x T     analyic opology  X .

N       x     X     x.

heorem 2.2. — I X is non-empy, he opological space X   is non-empy, locally separaed and locally compac. Moreover, 1) i is Hausdor i and only i X is separaed over k; 2) i is compac i and only i X is proper over k. Proo. — T          [5, §1.5]. S 1)  2)    ()  ()  [5, T 3.4.8  3.5.3]. □ Deinition 2.3. — L x       X  . T complee residue eld x  x        x         . T           ,         Hx. T             :  ,  f  X  Y       k,  f      f    X    Y  . F           X  X    X ,  X        X .

Remark 2.4. — T    X      x   :  x    ,    q    x    k . D  :

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

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1) I   ,    G’M f       C ()   C. T   X     X  X    X C  X C      . 2) I   ,    X     X  X    X C GCR

3) I   ,           X     B. I      X  . 6 Proposition 2.5. — I k be an algebraically closed eld and he absolue value on k nonrivial, hen he se o k-poins X k is dense in X  . A                Z   : Proposition 2.6. — Le X be a k-scheme o nie ype. For every consrucible se Z  X ,  X Z    X Z  where on he le-hand side he closure is aken wih respec he analyic opology and on he righ-hand side o he Zariski one. Proo. — S [39, E. XII, C 2.3]      [5, P 3.4.4]    . T           □   X  ≃ X C GCR.

2.1.3. Srucural shea. — L         X  . B    X  Akn     n.

Deinition 2.7. — L U  X      . A analyic uncion  U     f  U  x U x     x  U : 1) f x  x; 2)           U  x  U     д  kt       tn     U  ,   y  U ,    f y  д y   ( t       tn      Ank ). T k     U    OX U . T  U ▷ OX U        k     X  . F   x  X     x    . Deinition 2.8. — T n-dimensional analyic afne space    k       An  OAn  An k k

 6. F ,  X  Ak ,  Gauss norm   ∥ ∥  k t   R ,   a i t i   a i ,         k t . I        f ,    ∥ ∥     Ak  .

MÉMOIRES DE LA SMF 152

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 Remark 2.9. — I   ,   C  An    C n  C q      . I  ,   R    An     Cn  GCR q      R   f  Cn  f  z   f z. I        n f      B. S   [5, §1.5]  [54].

E         Ak  ,               k X   . 1) I X  f,     j  X  Ank    n. L I  OAn      X   I   OAn       I . C    k  X  , OX  j  OAn I  

O      OX           j.  2) F   k X    X  iN X i  f  . T  OXi  X i       OX   X  . O    OX       .

Deinition 2.10. — T  k  X   X   OX     analyicaion o X .         X       X  . A  f  Y  X  k        k   f   Y   X  . I       f   f  . 2.1.4. Exension o scalars

Deinition 2.11. — A analyic exension K  k             K q     k  K.

L K      k. L X   k      X K  X k K  K     K. L X K   K       K X K . Deinition 2.12. — T     X K  X        k  X K k  X K  X  

  exension o scalars map. I   ,            X .

Proposition 2.13. — Te map X K k is surjecive and opologically proper. Since he opological spaces X  and X K  are locally compac, he map X K k is closed.

Proo. — I   ,  k  R  K  C,   XCR    q    G . I       [6, §1.4]. □

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

80

T     K  :     k    f  Y  X   f K  YK  X K    K    f .

Deinition 2.14. — A K-poin  X    x  x      x  X        x  x  K.

L x  X      X    x  K    . T  x      x  X . L x K   K  X K      S K  S x  X   K X K .

Deinition 2.15. — T  x K    K  (   K      K)     X K   poin associaed o x and he embedding x  K.

2.1.5. Fibres. — L f  Y  X     k   . L x  X    , K  x       x K    X K    x. Proposition 2.16. — Keep he noaions jus inroduced. Ten: 1) Te map o scalars exension Y  K k  YK  Y  induces a homeomorphism     f   x Y  K k  YK X K x K 

2) For every analyic exension K ′ o k and every poin x ′  X K′ such ha X K ′ k x ′  x, he map induced by K ′ K k , is surjecive.

Y  K ′ k  f K′  x ′  f   x

Proo. — 1) I                  G . I   ,  [6, §1.4]. 2) L Ω  x ′       x ′   x Ω′     X Ω   x ′. T  x Ω′     x Ω     x    x  Ω  x ′ (        x ′   x). T    Y  ΩK ′

Y  K ′ k

Y  ΩK

Y  K k

f Ω  x Ω′   f K′  x ′  f   x

   

f Ω  x Ω   f K  x K   f   x

 K  x       x  x K     X K   x. T     : ,         (1);          YΩ X Ω x Ω    YK X K x K   

T   Y  K ′ k  f K′  x ′  f   x  .



Proposition 2.17. — Wih he noaions inroduced above, le y  y  Y  be poins such ha f y   f y . Ten, here exiss an analyic exension Ω o k and Ω-poins x Ω , x Ω  X Ω such ha:

MÉMOIRES DE LA SMF 152

2. PRELIMINARIES O HE LOCAL PAR

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1)  Ωk yi Ω   yi or i   ; 2) f Ω yΩ   f Ω yΩ .

Proo. — T      . Firs sep. – S  X  S k      k . T      :  f   Ω          yi   Ω  i     yΩ , yΩ     X Ω   y  y . Second sep. – L x  X     f y   f y    K  x    . L x K  X K     x. A  P 2.16   Y  K k  YK X K x K    f   x

  . T   yK  yK  YK   1) K k yiK   yi  i   ; 2) f K yK   f K yK .

C       K Y ′  YK X K x K , X ′  x K    □    f K  YK  X K . 2.2. Maximal compact subgroups. — L k   . 2.2.1. Subgroups. — L G   k  (i.e.   k    ). L m  G k G  G        G  G   . Deinition 2.18. — A  H  G       subgroup      : 1)    m       H     H   G  k G     H ; 2)    H       H ; 3)    e  Gk   H .

A  H     compac         G  .

L K      k   H  G    . T     H K  G K k H   G K

    G K . L G    k        G k X  X      . Deinition 2.19. — L H  G       x  X    . T H -orbi o x,  H  x,           H    x  G  k X  

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

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2.2.2. Archimedean deniion. — L k  R C   G   ()  k . Deinition 2.20. — I k  C  maximal compac subgroup  G     U  GC         GC. I k  R  maximal compac subgroup  G     U  G     CR U       GC. O      f   H       H C       Z. I    : ▷     H C  Z       ; ▷       H C  . I U       G,        U          G ≃ U R C    U  UR. A  T  G    R ( ,       U)     T  U       T C. 2.2.3. Non-archimedean deniion. — L k    G   k. C     G       G. A        Gk     [18], [19],     G     [5, C 5]  [57], [58]. L H   f k ◦        H  H k ◦ k    . C      U H  h  H    f д     f  k ◦  H  k ◦  H   k ◦      H.

Deinition 2.21. — A  H  G       maximal compac subgroup       H  U G    k ◦  G     k  ϕ  G k ◦ k  G.

T  U G             (    D 2.18),                  G  . T         . Proposition 2.22. — Wih he noaions inroduced above: 1) he se o k-raionals poins U Gk  U G Gk coincides wih he se o k ◦ poins Gk ◦ ; 2) or every analyic exension K o k, one has Kk U G  U Gk ◦ K ◦

as subses o G K ; 3) i k is algebraically closed and non-rivially valued, he se U Gk is dense in U G. Proo. — 1) L ϕд  A  k     k   д  Gk. T  д   U G     ϕд f      f  k ◦  G,    ϕд     ϕд  k ◦  G  k ◦ . MÉMOIRES DE LA SMF 152

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83

2) L f       f N     k ◦  k ◦  G. F   д  G  ,  f x     f  k ◦  G   fi x     i       N 

T        f       f N      K ◦   K ◦  G. 3) T       U G   f     B. T      [5, P 2.1.15]. □ T    [26]  [34]  ,      ,         Z. M : heorem 2.23. — Le G be a reducive k-group. Ten, here exis a nie separable exension k ′ o k, a Z-reducive group scheme G and an isomorphism o k ′-group schemes G k k ′ ≃ G Z k ′ 

T     C 3.1.5  T 3.6.53.6.6  [26]. 2.3. Plurisubharmonic unctions. — I       . I          ,    ,       . I   ,     P           R [60], [61], R  B [4], K [44], F  J [31]  T [66] (             ). T         [66, C 5]. M   ,                     P  . T         :  ,      M P          . H,        . O          CL  D [21]  B, F  J [17]. 2.3.1. Harmonic uncions. — L k       Ω  Ak     .

Deinition 2.24. — A   h  Ω  R     harmonic    x  Ω      U  x  Ω,    N    i       N     fi  U  OU       i  R   N ∑  i   fi  h U  i 

N           N       ,        . I                 C   . I            T ( [66, D 2.31]    [loc. ci., Tè 2.3.21]).

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

84

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

Proposition 2.25. — Le Ω be an open subse o he analyic afne line Ak  . Te ollowing properies are saised: 1) Harmonic uncions give rise o a shea o R-vecor spaces on Ak  . 2) I f is an inverible analyic uncion on Ω hen   f  is an harmonic uncion. 3) Le f  Ω ′  Ω be an analyic map beween open subses o Ak  ; or every harmonic map h on Ω he composie map h ◦ f is harmonic on Ω ′. 4) Le K be an analyic exension o k and ΩK  Kk Ω. For every harmonic uncion h  Ω  R composie uncion h ◦ K k  ΩK  R is harmonic. 5) (M P) I he open se Ω is conneced, hen an harmonic uncion h on Ω atains a global maximum i and only i i is consan. 6) I Ω is conneced, every non-consan harmonic uncion h  Ω  R is an open map.

Proo. — S 1) –4)   q   . 5) T M P        (    ) [25, C I, 4.14];             P 2.3.13  [66]. 6) I  f       Ω  . T   Ω    I  R ( )            .         :  I     ,    ;  b  R      I ,  h     b    M P. T        □ 2.3.2. Subharmonic uncions. — L k     Ω     Ak  .

Deinition 2.26. — A  u  Ω        subharmonic            Ω ′  Ω      h  Ω ′   u Ω′  h    ,  ,            . I      q       . T          Ω  q       ΩC    . I               T ( [66, D 3.1.5],      [loc.  ci., C 3.1.12]       [loc. ci., C 3.4.5] . Proposition 2.27. — Le Ω be an open subse o he analyic afne line A  . Te ollowing properies are saised: 1) Harmonic uncions are subharmonic. 2) I u v are subharmonic uncions on Ω and   are non-negaive real numbers, hen u  v and u v are subharmonic uncions. 3) I f is an analyic uncion on Ω hen   f  is subharmonic. 4) Le K be an analyic exension o k and ΩK  Kk Ω. For every subharmonic uncion u  Ω  R composie uncion u ◦ K k  ΩK  R is subharmonic. MÉMOIRES DE LA SMF 152

2. PRELIMINARIES O HE LOCAL PAR

85

5) Le f  Ω ′  Ω be an analyic map beween open subses o Ak  ; or every subharmonic map u on Ω he composie map u ◦ f is subharmonic on Ω ′. 6) (M P) I he open se Ω is conneced, hen a subharmonic uncion h on Ω atains a global maximum i and only i i is consan. 7) I ui i I is a locally bounded amily o subharmonic uncions on Ω, he is regularised upper envelope 7 is subharmonic. 8) Le u       un be subharmonic uncions on Ω and ϕ  Rn  R be a convex uncion ha is non-decreasing in each variable. Exend ϕ by coninuiy ino a uncion ϕ    n    Ten he uncion ϕ ◦ u       un   Ω    is subharmonic. Proo. — 1) F   . 2) S [66, P 3.1.8]. 3) F   . 4) I             q [25, C I, T 4.12]. I              [66, C 3.4.5]. 5) I       [25, C I, T 5.11]. I       [66, P 3.1.14]. 6) F   . 7) S [66, P 3.1.8]. 8) S [25, C I, T 4.16]. □ Proposition 2.28. — Le v  R    be a uncion. Te composie map     v ◦  t   Gm

is subharmonic i and only i one o he ollowing condiions are saised: ▷ v is idenically equal o ; ▷ v is real-valued and convex. Proo. —  I v       . I v     ,     v ◦  t     (8)    :   v    hi   i I

 hi    ai   bi          v. F  i  I   hi  t   ai  t   b  (). T   (7)    ,       v  t   i I hi  t    ()     ,    . 7. N        u i   i  I .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

86

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

 S  v    . S  t       v ◦  t    ,  v   . L a  b    ϕ        f    va  ϕa

 vb  ϕb

O    v   ϕ      a b. S   a b      v  ϕ   ,           a b. B   v    ϕ  ,     a b. T    ϕ  t     t            Gm    Ω  t  Gm  a   t   b 

 . 8 A     v ◦  t ,   v  ϕ ◦  t    M P  Ω. S     ,   . M,     v, v    ϕ    va  ϕa vb  ϕb  

    v    ϕ  .



2.3.3. Plurisubharmonic uncions. — L X   k . Deinition 2.29. — A  u  X        plurisubharmonic           K  k,    Ω  AK        Ω  X K ,    u ◦   Ω       Ω. I          ;                    . Proposition 2.30. — Le X be a k-analyic space. 1) I X is an open subse o he afne line Ak  he u is plurisubharmonic on X i and only i i is subharmonic. 2) I u v are plurisubharmonic uncions on X and   are non-negaive real numbers, hen u  v and u v are plurisubharmonic uncions. 3) I f is an analyic uncion on X hen   f  is plurisubharmonic. 8. I      . I       Ω          Ω    e b a C     C   x  Ak   a      t x    b     F          ,      C    x  Ak     t x    

  . T Ω  ,  . T   C         ,     ,  . O       C      k  ,   [5, P 3.1.8],   [5, T 3.2.1].

MÉMOIRES DE LA SMF 152

2. PRELIMINARIES O HE LOCAL PAR

87

4) Le K be an analyic exension o k and u  X    be a plurisubharmonic uncion. Ten he composie uncion u ◦ K k  X K    is plurisubharmonic. 5) Le f  X ′  X be an analyic map beween k-analyic spaces; or every plurisubharmonic map u on X he composie map u ◦ f is plurisubharmonic on X ′. 6) I ui i I is a locally bounded amily o plurisubharmonic uncions on X , he is regularised upper envelope is plurisubharmonic. 7) Le u       un be plurisubharmonic uncions on X and ϕ  Rn  R be a convex uncion which is non-decreasing in each variable. Exend ϕ by coninuiy ino a uncion ϕ    n   

Ten he uncion ϕ ◦ u       un   X    is plurisubharmonic.

Proo. — F  P 2.27.



2.3.4. Consrucion o invarian uncions. — L n      .

  Deinition 2.31. — A exended norm  An      An  R    k k    K  k,      K   Ank , K k

u

  R  u K  Ank K  K n  An k

     K  K n . I k  R C    u        Cn  . I k      u   ,     K  k,     K n  . Remark 2.32. — 1) I k  C         Cn    . 2) I k  R           Rn . 3) I k              ux   r  t  x     r n tn x   r       r n      t       tn     An . I      k n ,  d  

  x      x x k n   

T        k n   q. T  d          k n :              k n . Proposition 2.33. — Le k be non-archimedean. 1) A non-archimedean norm  on k n exends o a coninuous non-archimedean norm u   on An in a way such ha, i   are norms on k n , hen k    u  x      u x   d   x An    k

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

88

2) A coninuous non-archimedean exended norm is a plurisubharmonic uncion. Proo. — 1) T      . S        ,  ,     v       vn  k n     r       r n    x v       x nvn   r  x       r n x n    L ϕ       ϕ n  k n  k    . F x  An k

u  x  r  ϕ  x     r n ϕ n x

T u           . T      u   u    [35, P 2.1]       k. T          ( [11, 2.6.2, P 3]). 2) L u     . I        ,    k,     k       . T     k n  u   :     v       vn  k n     r       r n      x v       x nvn    r  x       r n x n   ( [11, 2.4.1 D 1  2.4.4 P 2]). L ϕ       ϕ n    . S k n     An   q  :  x  Akn  , k   ux   r  ϕ  x     r n ϕ n x  I   u  .



Proposition 2.34. — Suppose k algebraically closed. Le G be a reducive k-group and X an afne k-scheme o nie ype aced upon by G. Le U be a maximal compac subgroup o G. Ten, here exiss a coninuous, U-invarian, plurisubharmonic and opologically proper uncion u  X     .

Proo. — U   X   f   Gq ,    X  An      G  X  . I k  C  f           U. I k  ,  G    k ◦        U. L       k n   x  д  Gk ◦   д  x

S Gk ◦    ( ,      G  )  x     . T     Gk ◦     k n   P 2.33     q     u    An . T   u   ,      k   Gk ◦ . S Gk ◦     U, u   U  . □ 2.4. Minima on fbres and orbits. — I                                     .

MÉMOIRES DE LA SMF 152

2. PRELIMINARIES O HE LOCAL PAR

89

2.4.1. Minima on bres Deinition 2.35. — L f  X  Y       u  X     . T   u-minima on f -bres f u  Y        y  Y   ux

f uy 

f x y

L k       f  X  Y     k   . L f   X   Y      k    f . L K      k   f K  X   Y      K      K. Proposition 2.36. — Le u  X     be a uncion. Wih he noaions jus inroduced: f K u ◦ X K k   f u ◦ Y  K k  Proo. — T     ,    y K  YK ,        Y  K k  f K  y K   f   y

 y  Y  K k y K    ( P 2.162)).



2.4.2. Minima on orbis. — L X   k          k  G. Deinition 2.37. — L H  G      u  X      . T   u-minima on H -orbis u H  X      ,   x  X  ,  u H x  ′  ux ′

I   H 

G 

 uG   u

x H x

G 

.

Remark 2.38. — L   G k X  X     k     G  X . L    G  k X   X       k . D  H   H   G  k X   X  

      . W  ,  , u H  H  u ◦  

Proposition 2.39. — Le u  X     be a uncion. Le K be an analyic exension   o k and consider he subgroup H K  G K k H  o G K . Ten, u ◦ X K k H K  u H ◦ X K k  Proo. — T   P 2.36   R 2.38.



SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

90

Proposition 2.40. — Le u  X      be an upper semi-coninuous uncion. Ten, 1) he uncion uG  X     is upper semi-coninuous; 2) i u is coninuous, he subse   X G u  x  X   uG x  ux    is closed.

Proo. — 1) I         uG         x  uд  x  д  GC. I   ,   P 2.39,         . S      k    k   . I    k  Gk    G  . A      u    x  X  , uG x  ′ ux   uд  x x G x

д G k 

C             X            uд  x  uд  x  д  Gk. □ 2) F     uG  u. 3. Kemp-Ness theory L k    . F        : ▷ I f  X  Y     k,   f    k  f   X   Y    f ; ▷ L X   k         k  G. I x  X         G  x   G   x. 3.1. Set-theoretic properties o the analytifcation o the quotient. — T         ()  ()  T 1.6. L          1.41.5. Proposition 3.1. — Wih he noaion inroduced above: 1) he morphism   X   Y  is surjecive and G-invarian; 2) or every x x ′  X  ,  x     x  

i and only i G  x   G  x  , ∅

3) or every poin x  X  here exiss a unique closed orbi conained in G  x. I ,    x x ′  X        q     G  x   q     G  x ′ . B      P 3.1   :

MÉMOIRES DE LA SMF 152

3. KEMPFNESS HEORY

91

Corollary 3.2. — Wih he noaions inroduced above, le X ′ be a G-sable closed subscheme o X and Y ′ is caegorical quoien by G. Ten he induced morphism o k-analyic spaces Y ′  Y  is injecive. Proo o Proposiion 3.1. — 1) C  P 1.4. 2) C   x   x   X  :    

 x     x    G  x   G  x  , ∅

 S       G  x   G  x      y. B    G   ,  x     y   x    S  x     x  . F         x  , x   k  . A  P 2.17      K  k  K  x K , x K  X K  : ▷ K k x iK   x i  i   ;

▷  K x K    K x K  (  K  X K  YK     K     ). S              ,   AGKK  AG k K  G K   K    G    . T  f K YK    q   f K X K   K  G K . T,      K,       x   x   X   k. L x   x   X   k      X   X      k      X .     : ▷    X   Y     k       k   X  Y ; ▷ G   x i     k x i  X         G   x i (i   ) . F i   :     G   x i   G   x i  T    x      x      x      x  . A  T 1.4       : G   x    G   x   , ∅

F i      G   x i      X     Z              Z  (P 2.6):   G   x i     G   x i   G   x i 

S       G   x  , G   x           G   x  , G   x    . 3) F  2):    x  X     y  y  G  x. S     G    y    y . I       y  y  ,  (2) f  G  y  G  y ,   . □ SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

92

3.2. Comparison o minima 3.2.1. Saemens. — L          1.4–1.5      T 1.9: heorem 3.3. — Wih he noaion inroduced above, le u  X     be a plurisubharmonic uncion which is invarian under he acion o a maximal compac subgroup o G. For every poin x  X  , ux ′  ′ ux ′  ′ x G x

 x  x 

Corollary 3.4. — Le u  X     be a plurisubharmonic uncion which is invarian under he acion o a maximal compac subgroup o G. Ten, 1) a poin x is u-minimal on  -bres i and only i i is u-minimal on G-orbis; 2) X  u  X G u; 3) i u is moreover coninuous, he se o u-minimal poins on  -bres X  u is closed. Proo o he Corollary. — C     u      u    G. S 3)   P 2.402). □ I    T 3.3  : heorem 3.5. — Wih he noaion previously inroduced, or every poin x  X  here exiss a poin x  ha belongs o he unique closed orbi conained in G  x and such ha ux    ux. L      T 3.3. Proo o Teorem 3.3. — F   x  X  , 

 y  x 

uy   uy y G x

I      q. L x x ′  X      x ′   x. A T 3.5    x ′,     x ′     q     G  x ′    ux ′   ux ′. B ,  x ′    x ′   x

 G  x ′   q     G  x. T, ux ′  ux ′  

 uy   uy   uy

y G x ′

y G x

y G x

   q         u. S x ′  ,  uy   uy  y  x 

     T 3.3.

y G x

T            T 3.5.

MÉMOIRES DE LA SMF 152



3. KEMPFNESS HEORY

93

3.2.2. Parabolic subgroups conaining desabilizing one-parameer subgroups. — D      . L k             k G   f k X   . L S  X    G   X . T       K             ( [45, T 3.4]): heorem 3.6. — Le x  X k be k-poin o X such ha G  x  S , ∅

Ten, here exiss a parabolic subgroup P  PS x o G saisying he ollowing propery: or every maximal orus T  P here exiss a one-parameer subgroup T  Gm  T such ha he limi  t  x exiss 9 and belongs o S.

t 

3.2.3. Desabilizing one-parameer subgroups: archimedean case. — L G    ()     U  GC    . T,    R  U   U R C  G  U R  U. M,   T  G    R     T C  U       T C. L X  S A    f          G. L S  X   G Z  . Lemma 3.7. — Le x  X C be a poin such ha G  x mees S. Ten, here exiss a oneparameer subgroup   Gm  G saisying he ollowing properies: ▷ he limi poin  t  x exiss and belongs o S; t 

▷ he image o U is conained in U.

T      [46]  X  AnC      G  S  . I          Gq  f  X  An   f    S.

Proo. — W      KN. A  T 3.6      P  G    :     T  P      T  Gm  T       T t  x

t 

    S. L P           G   U . L T        P  P     R. A           T         G. T  T 3.6        Gm  T    q . □ 9. N    k   x  Gm  X , t  t   x      k   x  A  X   , t  t   x   x 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

94

3.2.4. Desabilizing one-parameer subgroups: non-archimedean case. — L k             k ◦    . S k  . L G    k ◦   G   . A     G    U      Gmk ◦  G       Gm   U   G. L X  S A   f k         G   S  X   G  . Lemma 3.8. — Le x  X k be a poin such ha G  x mees S. Ten, here exiss a oneparameer subgroup   Gmk ◦  G such ha he limi poin on he generic bre  t  x

t 

exiss and belongs o S.

Proo. — B T 3.6      P  G     :     T   G      T  Gm  T       T t  x

t 

    S. D  P G        G:     k ◦ [34, E XXVI, Tè 3.3–C 3.5]. B         q   P  G    P. L T      P   T    . 10 L   Gm  T       T 3.6. S k    ,   T           q        Gmk ◦  T    q . □

3.2.5. End o proo o Teorem 3.5. — L x  X   U      G     u. U    k   : ▷ archimedean case: k  C; ▷ non-archimedean case: k       x  k. L S   q     G  x. A  L 3.73.8        Gm  G    : ▷    x    t  x     S; t 

▷    U    U.

10. B [34, E XII, Tè 1.7]   (    )      q        ,       S  N     s  S  s        G S S s  s         s  s. I         Q     H      H [10, C 11.3]:  ,     Q  q     H . O   ,           [34, E XIX, C 2.6]. T        P  ()   S k ◦ :  k    P    .

MÉMOIRES DE LA SMF 152

3. KEMPFNESS HEORY

95

L   ux    ux. T  t  t  x      k  x  Ak  X    x   x  . T    t   ux     u x  Ak    t  ut  x 

  (     u ◦  x )  U. B  M P,   u x t  u x   ux   t 

A  P 2.28   v x  R   

  v x  t   u x t

   q        . I  ,   v x      u x t  ux     t 

 

 v x    . I , ux      v x    v x   ux  

     T 3.5.



3.3. Analytic topology o the quotient 3.3.1. Saemen. — I      3)  T 1.6: Proposition 3.9. — Le F  X  be a closed G-sable subse o X  . Ten is projecion  F  is closed in Y  . C   C 3.2: Corollary 3.10. — Le X ′ be a G-sable closed subscheme o X and le Y ′ be is caegorical quoien by G. Te induced morphism o k-analyic spaces Y ′  Y  is a homeomorphism ono a closed subse o Y  . T           P 3.9. 3.3.2. Minimal poins on afne cones. — T   P 3.9                  f . D    . L   Ad  B Bd  A d 

d 

 ()  k       k A , B    (i.e.    k ). L X  S A  Y  S B   . L ϕ  A  B      D     k,      k     d  ,  Bd   Ad D 

T  ϕ     k f  X  Y . L f   X   Y      k    f . SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

96

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

Deinition 3.11. — L u  X   R   . 1) A  x  X      u-minimal on f -bre     x ′    f x ′  f  x   ux ′  ux. T   u   f     X f u.

2) L h  A  k X   X              A. T  u  X   R     -homogeneous     z  A  k  X ,       u hz    z  u  z    ,      A  k X  .

Proposition 3.12. — Wih he noaion inroduced above, le u  X   R be a coninuous, -homogeneous and opologically proper uncion. I X f u is closed in X  , hen he resricion o f o X f u, is opologically proper.

f   X f u  Y  

Proo o Proposiion 3.12. — T       ,         k  R      . 11 C   b      bn  B   b    ,    Y    f  An   S kt       tn      kt       tn     k   kt       tn         t     .     f   f  X f u  X  . A  ,      f  X      . T    q   x i i N  X        ux i     i  . O   f x i i N        An    ux i  ,    i  N. S     k  ,   i  N   i  k    i   ux i . D   q  X   xi xi   i B   u   xi       f . M   x i ’       x  ux  . B q  12 ,      q  x i      x . B : ▷ x  u  f ; ▷ u x    . 11. A   K  k        K  K  R          . T       :       . O                k  R  . A            ux i       k . 12. I          ;           q      [55].

MÉMOIRES DE LA SMF 152

3. KEMPFNESS HEORY

97

T    . I   f  X  An       f       fn    f   D  (    ϕ     D). T,   i  N         n,  f   x i  

 f  x i   f  x i    i  ux i 

T  f  x i       ,      f  x i      i   . B  ux i     i  ,  

  f   x i   

i   n



i   n

 f  x i    ux i 

  f  x    . S x   u   f ,            S A  X . x    . □ T   u  u x       u 3.3.3. Reducing o he case o he afne spaces. — G      P 3.9         1.41.5. O       X   f  Ank . L X   S A  X   S A  kf  (  )        k G   i  X   X     Gq . F      Y    q  X   G      X   Y   q . T    k X

i



Y

X 

j

Y

 ,  j       q. C  3.2 f  j  Y  Y   . I ,    F  X  ,     F   j    ◦ iF  

S     P 3.9     k  X  . I F    G   X  ,  iF     G   X       iF     Y . T   F   j    ◦ iF     Y . O       f     Gq  i  X  Ank . L X     Ank  S kt       tn   G. S    G  X  ,    G   k   A  kt       tn    . I ,    G AG      AG  A         k . 3.3.4. Using Kemp-Ness heory. — T   P 3.9            k:        k  C           k G        k ◦  G.

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

98

L U          u  X   R    ,  , ,   U (   P 2.34).   P 3.12    u         u     X  u  . S u  ,        ,    ,   C 3.4,    u          u   G,     . N P 3.12       X  u  Y 

  . A u   ,    . T   X  u  Y    ,       X  u    . O     :    G  F  X  ,   (3.1)  F  X  u   F 

       X  u  Y   ,    . L   (3.1).  C.  O        x  F    u     x ′  F    x   x ′. S F     G ,        G  x    x. L x ′  G  x  u   G:      u   . S u   G     ,   x ′  u   ;           x    x ′   x,      (3.1). □ 3.4. Continuity o minima on the quotient. — L X   f k       k G. L Y    q  X  G     X  Y  q . L u  X                     G. C  uncion o u-minima on  -bres  u  Y        y  Y    uy   ux  x y

Proposition 3.13. — Te map  u  Y     is upper semi-coninuous. I he uncion u is coninuous and opologically proper, hen: 1) he resricion o  o X  u  X G u is opologically proper and surjecive ono Y  ; 2) he uncion  u is coninuous on Y  . Proo. —        u,             V  y  Y    uy     . T 3.3 ,    x  X  ,  u x 

MÉMOIRES DE LA SMF 152



 x ′  x 

ux ′  uG x  ′ ux ′ x G x

3. KEMPFNESS HEORY

99

I       :

    V     y  Y    uy      x  X    u x      x  X   uG x   

T  uG  X    , x  x ′ G x ux ′    ( P 2.40). T  q   U    V    G    X  . B C 1.7 (4), V   U       Y  . S  u      . 1) T     X  u  Y          u. I       X  u  Y    . L K      Y  . T   u   ,      K:      uy   y K

T     K      x  X    u x   ,   f      x  X    u x     X  u

 . B           u  u   X  u,    x  X  u   u x     x  X  u  ux   

T           X  u    u    . 2) T   X  u           X  ,      X  u  Y    (   ). T q u

X  u 

    u

   u  .

X  u 



3.5. Comparison with the result o Kemp-Ness 3.5.1. Special plurisubharmonic uncions. — I        . W    q    T 1.9         KN     ,    . L X     . Deinition 3.14. — A  u  X      special plurisubharmonic             D  X ,  D  z  C  z      ,   u ◦   .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

100

Proposition 3.15. — Special plurisubhamornic uncions enjoy he ollowing properies:  i    is a posiive real number and u is a special plurisubharmonic uncion u, u is special plurisubharmonic; i u v are special plurisubharmonic, hen u  v is special plurisubharmonic;  i X is a conneced analyic curve and f is a non-consan holomorphic uncion hen   f  is a special (pluri)subharmonic uncion;  i f  X ′  X is a holomorphic map wih discree bres and u is a special plurisubharmonic uncion on X , hen f u is special plurisubharmonic on X ′;  srongly plurisubharmonic uncions are special plurisubharmonic. Example 3.16 1) T   4)  :   p       ℓp ,  p  ∥x ∥ℓp   x  p      x n p

    Cn          . I p ,  ( n  )  Kä       OPn     . { } 2) T    ℓ    ∥x ∥ℓ     x       x n     . L G          f  X   . heorem 3.17. — Le u  X C    be a special plurisubharmonic uncion invarian under he acion o a maximal compac subgroup U o G. Le x  X C be a poin which is u-minimal on is G-orbi. Ten, 1) he orbi G  x is closed; 2) le G x be he sabilizer o x; he ollowing inclusion is an equaliy:   kд  k  U д  G x C  д  GC  д  x  X G u 

I  ,       G    U. Corollary 3.18. — Le u  X C    be a coninuous opologically proper, special plurisubharmonic uncion, invarian under he acion o a maximal compac subgroup U o G. Ten, he coninuous map induced by  , X  u U  Y 

is a homeomorphism.

Proo. — 1) B       x      S   q     G  x. A  L 3.7         Gm  G    : ▷    x    t  x     S; t 

▷    U    U.

MÉMOIRES DE LA SMF 152

3. KEMPFNESS HEORY

101

L   ux    ux. T  t  t  x      x  Ak  X       x     . C    ux    t   u x  C    u x t  ut  x 

T  u x   ()  U. A   M  P,    u x   ux   t 

P 2.28     v x  R   

    v x  t   u x t 

   q    . A u x   ,     I , v x     I . S   v x      u x t  ux     t 

 

  v x    . T ux    v x   v x   ux      x. 2) S     G    T . A  1)   T  x  x  . R X  T  x  T  T Tx ( Tx     x)        x  ,    x  T  X 

t  t  x

 . T  u x t  ut x     T C         U. I T C U  Rn ( n     T )   :  n    T C U  C  U  Rn  z       zn    z        zn  

S u x      U,   (   )     v  Rn  R         u x . M,  u x   , v        Rn . T   x  u      v          Rn .               :    ,          Rn  ,     v           t  t   . L             G. L д  GC    д  x   u    G. B C’     k  U  t  T C   д  kt  T      G   T C  U       T . S   u  U, uд  x  ukt  x  ut  x SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

102

 t  x    u    G. B        k ′  U T C  t ′  Tx C   t  k ′t ′. T   д  kt  kk ′t ′  kд  k  U д  G x C    .



4. Metric on GI quotients 4.1. Extended metrics 4.1.1. Deniion. — L X   k     L      . C     L  X , VL  SX S OX L  F  k S  S   VL          x s    S  x  X S     s  S x  L. C  k  X   VL     X  VL.

Deinition 4.1. — A  ∥∥L  VL   R   exended meric on L       K  k,    ∥ ∥L

∥∥L K  VL K  VL   R         L:   K x  X K   s  x  L  ∥s ∥L x  ∥x s∥L K      K  x  L. A                VL  . Remark 4.2. — L ∥∥L      L. F     U  X       ∥s ∥L  U  R , x  ∥s ∥L x. O   ,   ,      U  X     s  U  L  ,    ∥s ∥LU  U  R       x  U : ▷ ∥s ∥LU x       sx  ; ▷ ∥s ∥LU x  ∥s ∥L x     k; ▷ ∥s ∥LU V  ∥s ∥LV     V  U . T     ∥s ∥LU       L. I   ,                 . I   ,                .

MÉMOIRES DE LA SMF 152

4. MERIC ON GI UOIENS

103

4.1.2. Consrucions. — U    (,  …)       . F               . L ∥∥L      L, K     k, x  X K  K   X  s  x  L. F   ϕ  x  L    s  x  L,  ∥ϕ ∥L  K x 



t x  L 

ϕt ∥t ∥L K x



∥s n ∥L n  K x  ∥s ∥L K xn 

T   ∥ϕ ∥L  K x       x ϕ  VL   :      L     . A       L n   n    ∥∥L . L K      k. I ∥∥L      L    ∥∥L ◦ V L  K k  VLK  R

       L K  L  X K  X k K.

4.1.3. Exended meric associaed o inegral models. — S k   X . L X    k ◦   X ,  ,   k ◦       k   X ≃ X k ◦ k. L L      X         L  X   ≃ L. T                      . D    ∥∥ L    . L K       k   x  X K   K   X . T    K ◦  K            x    K ◦    x  S K ◦  X. T K ◦   x L   K ◦     :     s    x L. E  s  x  L ≃  x L K ◦ K   s  s    q   K. S: ∥s ∥ L K x  K 

T   ∥s ∥ L K x       x s  VL      ∥∥ L  VL   R 

           L. T              :         ∥∥ L           L . I K        ∥∥L ◦ K k         LK ◦  L  XK ◦  X k ◦ K ◦ . S k     (     k ◦  )   L   . T     S X  L d    VL   SX S OX L  X d 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

104

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

 ,                  S X  OX . F   x  X  VL   X u Lx 



f  X L

 f x

F   f       fn   k ◦   X L, u Lx    fi x i  n

Proposition 4.3. — Suppose L generaed by is global secions and L very ample. Wih he noaions inroduced above, ∥∥ L  u L ◦   I     ∥∥ L  VL        ,      VL   . Proo. — L K      K ◦    . L x   K   X   x  q K ◦    X   x. S L      ,      f    X L    x f       K ◦   x L. C   s    x L     s   x f    . F   K  s  s  :   ∥s ∥ L K x  K . T,      f  x s  K  f  x s    K  ∥s ∥ L K x K K F    f   X L,

     f x s  K  f x s    K  ∥s ∥ L K x K K

 f x s     k ◦ . T   .



Corollary 4.4. — I L is ample, hen he coninuous map  ∥∥ L  VL      is plurisubharmonic. 4.2. Extended metric on the quotient 4.2.1. Deniion o he exended meric. — L X    k        k G   G    L. T  k  G   X  L d G  A  X  L d  AG  d 

d 

   . D  X       . T   AG  A   G   k   X   Y  P AG  MÉMOIRES DE LA SMF 152

4. MERIC ON GI UOIENS

105

  Y   q  X   G. S AG    ,  k Y  :     D           M D  Y        ϕ D    M D  L D X     q   G. T  ϕ D       k   VM D   D  VL D X 

L ∥∥L       L     t  VM D    ∥t ∥M D 

 ∥s ∥L D   

 D s t

       s  VL D   . X  Proposition 4.5. — Wih he noaion inroduced here above, he uncion ∥∥M D is an exended meric on M D . Proo. — L K      k       . L y  Y K   K  Y  t  y  M D    y. S Y K    YK     ∥∥L  , ∥t ∥M D  K y 



x X  K 

∥ t ∥L D  K x   

 x y

I      ∥∥M D      ,         ∥∥M D    . U      M D ,    M D          . I f        s  Y  M D    y  Y  , ∥t ∥M D y  

T        t  Y  M D   M D     ϕ D   G   t  X  L D G  L D          X  X  . F   y  Y  , ∥t ∥M D y   ∥ t ∥L D x x X 

            X     □  ∥∥L . heorem 4.6. — Suppose ha: 1) he exended meric ∥∥L is invarian under a maximal compac subgroup o G; 2) he dual exended meric ∥∥L   VL    R is a plurisubharmonic uncion.

Ten he exended meric ∥∥M D is coninuous.

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

106

4.2.2. Passing o he afne cones. — I              . T        L  MD . S D   LD  MD   . C    k    :    X  L d D   AGD  X  M Dd   X  L d D G  AD  d 

d 

d 

T k X  Y          AD  AGD . T   AGD  AD     k,   S AD  Y  S AG    X D

     G ( [63, T 3]).   Y   q  X T         :  VLD X 

VLD 

D  MD

VM D 

 L D

 X

 

Y

  L D   M D   . T   L D   M D    ,            VLD   VM D . T    ∥∥L D  ∥∥M D    u L D  u M D    Y . B      ∥∥M D ,   y  Y ,   X (4.1)

u M D y 

 u L D x  u L D y

 x y

(          ). Proo o Teorem 4.6. — T  u L D        ∥∥L D :   ,  ,          G. A  P 3.13   u M D  , □     ∥∥M D   . 4.3. Compatibility with entire models 4.3.1. Noaion and saemens. — S  k            (     k ◦  ). L G    k ◦        k ◦  X q    G   L. H      S’           k ◦   . Deinition 4.7. — A   A     japanese       K ′     K  FA     A  K ′   A    (i.e.   A). A  A     universally japanese    A     .

MÉMOIRES DE LA SMF 152

4. MERIC ON GI UOIENS

107

F ,      k     k      Qp   k  Ft    F [37, C 7.7.4]. T     S [63, T 2] :   k ◦   G   AG   X Ld  G  A   X Ld  d 

d 

   . D  X      ,  Y   q    X  Y   . F  D    MD       Y   LD   ϕ D    MD  LD X

 Gq    .

D      k       k ◦     (  X k ◦ k     X ). L ∥∥ L       L   L. Deinition 4.8. — W    ,  Ω      k       . A   x  XΩ : 1) minimal      s  x  L    д  GΩ,  ∥s ∥ L Ω x  ∥д  s ∥ L Ω д  x

T        s.   x       2) residually semi-sable    13 x  XΩ       Ω     G k ◦ Ω. X k ◦ Ω Ω

L x  X       Ω         x. T  x   (.  )    Ω x Ω  XΩ   (.  .) heorem 4.9. — Suppose ha k ◦ is universally japanese. Wih he noaions inroduced above, or every semi-sable poin x  X  he ollowing are equivalen: 1) x is minimal; 2) x is residually semi-sable. Corollary 4.10. — Under he hypoheses o Teorem 4.9, le Ω be an analyic exension o k which is algebraically closed and non-rivially valued. Le x  X Ω be a semi-sable poin. Ten, here exiss a semi-sable minimal poin x   X Ω lying in he closure o he orbi o x and whose orbi is closed (in X  ). I        k      Qp ,      B [20, P 1]. W      B     B . 13. S X  ,         x    Ω◦     x  S Ω◦  X. T reducion o x ,  x,      x      Ω◦ .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

108

T           . A  q,      M D : 1)    ∥∥ MD      MD ; 2)    ∥∥M D      (  4.2.1).

heorem 4.11. — Suppose ha k ◦ is universally japanese. Wih he noaion inroduced above, he merics ∥∥M D and ∥∥ MD coincide. In paricular, or every analyic exension Ω o k which is algebraically closed and non rivially valued, ∥t ∥ MD  Ω y   ∥ t ∥ LD  Ω x  x y

where he supremum is ranging on he semi-sable Ω-poins o X . 4.3.2. Some more noaions. — S    D       LD  MD   . B     4.2.2. A  (4.1),   y  Y , u M D y  u L D y 

 u L D x

 x y

  y  Y  C    u LD , u MD   x  X      f x  u M y  дy   u LD x 

S

D

f  X LD 

LD

д  Y MD 

 MD    ,   P 4.3,   ∥∥ LD  u LD ◦  L D



∥∥ MD  u MD ◦  M D 

T   Y MD  ≃  X L G     Y MD    X LD .  , T,  x  X   (4.1) u MD x  u LD x

 be a poin ha does no Lemma 4.12. — Wih he noaions inroduced above, le x  X , belong o he analyicaion o verex OX o he afne cone X    S OX  S X  OX   X X  L d D  X  .

d 

Le x be he associaed poin o Te ollowing are equivalen: 1) he poin x is residually semi-sable;  x. 2) u LD x  u MD 

Proo. — U   x    u LD x  . L Ω         x    x  S Ω◦  X        x      . 1)  2). S MD        G   f   X LD     x f       Ω◦   x LD . I  ,   f x  Ω◦   . T    u MD x    u LD x MÉMOIRES DE LA SMF 152

4. MERIC ON GI UOIENS

109

2)  1). T q u MD   x       G     . I  f   X LD    f x  Ω◦   ,     Ω    x  x  . □ Proo o Teorem 4.11. — S       ∥∥ L, ∥∥ MD  ∥∥M D       L  MD ,      LD  MD  . T q   ∥∥M D  ∥∥ MD  q   q   u MD  u M D . F  y  Y ,  q (4.1)  u MD y  u M D y 

 u LD x

 x y

I      q. L y  Y   . S      ,        x     y. u LD  X A  T 4.9   x    x  X    . L 4.122)    u LD x  u MD x  u MD y I ,

u MD y 

 u LD x ′

 x ′ y



Proo o Teorem 4.9. — 1)  2)   q (4.1)  L 4.122).   f     k ◦  X    2)  . D  X       LD ,  ,      k ◦   AD   X Ld D  d 

U     x  u LD x  . T  q    x     x  X  k          k ◦    X  OX  S  X OX  X. A       x    . T   A       x         K Xk ◦ K. HM        x ,      Ω  K        Gm Ω  G k ◦ Ω

     x :   ,  OX  S  X OX    ,   f  X   x  OX k ◦ Ω   t t 

A  [34, E XI, Tè 4.1]  k ◦            k ◦   G    k ◦ . S    Ω◦  ,  “H’ L” [34, E XI, C 1.11]            T  G k ◦ Ω◦  SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

110

CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

 T       (  ). T,    Ω    ,       T     Gm Ω◦ .   T    Ω    Gm Ω  G Ω    U  ◦       G Ω    Ω   G k ◦ Ω◦ .  C   ϕ x  Gm Ω  R   ϕ x t  u LD t  x

T  ϕ x           U. D     x  R  R   :    t  Gm Ω,    x  t    ϕ x t

T   x   ,    x   u LD    G ,       :  x    u LD x S u LD x      x   .      f       x   ,       x. T  Gm Ω◦     Ω◦  E   X LD   Ω◦     . T E       ,  E Em  

 ,    m  Z, Em  f  E  t  f  t m f . F m  Z  m Z

um x    f x f  Em

 T   ,    t  Gm Ω, { } ϕ x t  u LD t  x   t m um x  m Z

            t , { }  x     m   um x  m Z um x ,

B  u LD x      m,   um x  . F,     m  ,    um x              x. S           : ▷  m    m   um x  m  ; ▷  m    m   um x   um x  ; ▷  m    m   um x           um xm    um xm  . T  x              ] {  u x } [ m     m  m T     T 4.9   T 1.17. □

MÉMOIRES DE LA SMF 152

4. MERIC ON GI UOIENS

111

Proo o Corollary 4.10. — U    ,  k  Ω  k     . M,    x      X  . C  Z   Z  G x  X,       k ◦     Z  S k ◦  . T   Z       G. I,              x 



G  G k ◦ X  X

  x  S Ω◦  X      x           G k ◦ X  X        G  X. T  X  Z      Z      k ◦ .

Claim. — Te srucural morphism   X  Z  S k ◦ is surjecive.

k  x (      Proo o he claim. —    x  X  ). S   u LD        x   OX  X ,   u LD       y  G   x (     a priori       k). T  y  X   y          D 4.8, ,   T 4.9,  . I  ,   y  S y◦  X          X  Z,

X  Z 

X

S y◦

S k ◦

y

I      X  Z  S k ◦  .



S       ,     (  k    ). T      (    T 4.9)      . □

T           [38, 17.6.2  18.5.11 (’)] ,     ,   : Lemma 4.13. — Le k be a complee non-archimedean eld, which is non-rivially valued and algebraically closed. Le S be a a scheme o nie ype over k ◦ . I he srucural morphism   S  S k ◦ is surjecive, hen here exiss a secion s  S k ◦  S o .

Proo. — I f    S  f,   S  S A  A    k ◦    . C  k    A  A k ◦ k. S A   ,          A  A. F  f  A :   ∥ f ∥ A     f   A   k   T        S  S k ◦      ∥∥ A         A. T ∥∥ A      A. L A   A     ∥∥ A. SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

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CHAPER 3. KEMPFNESS HEORY IN NONARCHIMEDEAN GEOMERY

L S      S   S    . T  specrum    ( [5, §1.2])    B k A     s  S    f s  ∥ f ∥ A   f  A  MA

     ,   [5, T 1.2.1],    MA   S A    f      . M,  B k A   Sk   B ( [57, 1.2.4]):  k   ,  k MA  □   MA. I ,        .

MÉMOIRES DE LA SMF 152

CHAPER 4 HEIGHS ON GI QUOIENS: FURHER RESULS

I            GI q,   F F (    ,   q   C  1),                 C 1. T     . S 1      :      ,      C 3         F F (T 1.5)  . I S 2         q. F             :   ,        S 4    . S,      F F,                        GI q. W                . I S 3          GI q              . F          q            B, G  Z. H,                     B. I S 4                      C       C 1 ( T 2.1). T                 (      ). I    ,       (       SL ).

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CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

1. Statement o the main results 1.1. Notation. — L K      oK     . L X      oK        oK   1 G. S  X  q   G    L. A      S [63, T 2]   oK   G,   AG   X Ld  G  A   X Ld  d  d     . D  X      , i.e.     x  X       d     G   s  Ld      x. T   AG  A   G   oK ,

  X  Y  P AG

  Y   q  X  G [63, T 4]. S AG    ,  oK  Y  :     D           MD  Y      ,  ϕ D    MD  LD X

   q   G.    “” ,       K  C     L X C     ∥∥ L . S      : ▷ S:  Kä     ∥∥ L   (    ); q      U  X C    s  U  L     ∥s ∥ L  ; ▷ I:   ∥∥ L             G C. S      ∥∥ L    K  C     . D  L     . L   K  C    . D    MD  :    y  Y C    t  y  MD  ∥t ∥ MD  y   ∥ t ∥ LD  x  x y

heorem 1.1 (c. T 1.13  C 3). — Under he assumpions made on he meric ∥∥ L (semi-posiiviy and invariance under he acion o a maximal compac subgroup) he meric ∥∥ MD  is coninuous.

T    ∥∥ MD     K  C       .

1. L S   . A S   G    reducive (   S -reducive group)       : 1) G  f,       S ,  2)     s  S Ω  S ( Ω     )   G s  G S s       Ω.

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE MAIN RESULS

115

Deinition 1.2. — W    ,   M D      . C   h M  YQ  R ,   Q  YQ,   h M Q  h M D Q D      D. T  h M    heigh on he quoien wih respec o X, L and G. 1.2. Instability measure. — L v  VK    K. I   v     ∥∥ Lv           L.

Deinition 1.3. — L x   Cv   X. T (v-adic) insabiliy measure  v x    

д  GCv 

x  L 

∥д  s ∥ Lv д  x    ∥s ∥ Lv x

  . T       s.  s  T  x     minimal    v (      ∥∥ Lv     G)     , v x  . Proposition 1.4. — Le x be a Cv -poin o X. Ten, 1) he insabiliy measure v x akes he value  i and only i he poin x is no semisable; 2) i v is a non-archimedean place over a prime number p, he insabiliy measure v x akes he value  i and only i he poin x is residually semi-sable, ha is, he reducion 2 x o x is a semi-sable F p -poin o X oK F p under he acion o G oK F p . T    q  T 1.9  T 4.9  C  3. 1.3. Statement and proo o the Fundamental Formula heorem 1.5 (F F). — Le P  X K be a semi-sable K-poin. Ten he insabiliy measures v P are almos all zero and ∑    h L P  v P  h M  P  K  Q v V K

Proo. — L P  . T,

(1.1)

X K

   K  X   t   P MD    

∑     K  Qh MD  P    ∥t ∥ MD v  P ∑

v VK



v VK

 



 P ′  P 

∥ t ∥ LD v P ′

2. S X  ,         x    ov   X,  ov       Cv .     p    F p  x  X    reducion  x .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

116

    q         ∥∥ MD       T 1.17  C 3    . A   T 1.16  C 3: ∑      ∥ t ∥ LD v д  P K  Qh MD  P  д  GCv 

v VK





v VK

  

д  GCv 

 D

∑

v VK



∥ t ∥ LD v д  P ∥ t ∥ LD v P

  ∥ t ∥ LD v P

 v P  K  Qh L P  v VK

      v    P (   t  G ,  д   t   t   д  GCv ). T      F  F. □ 1.4. Te case o a projective space. — L F       oK . S   oK   G    F  ,      K  C,    ∥∥ F           U  G C. T oK   G      X  P F    q       L  O. F     K  C     O X C   FS  ∥∥ O       ∥∥ F . B ,   ∥∥ O       G C      . L L                1.1. L v     K. L x      F oK Cv  x   Cv   X. B ,   v x  



д  GCv 

∥д  x ∥ Fv , ∥x ∥ Fv

   ∥∥ Fv     F oK Cv (    ∥∥ Fv  ). I    F F   : Corollary 1.6. — Le v be a non-zero vecor in F oK K and le P  v be he associaed K-poin o X. I he poin P is semi-sable, hen: ∑    ∥д  x ∥ Fv h M  P  h OF  v    д  GCv  ∥x ∥ Fv v VK ∑    ∥д  x ∥ Fv  v VK

д  GCv 

I        B [20, P 5].

MÉMOIRES DE LA SMF 152

1. SAEMEN OF HE MAIN RESULS

117

M              . L   K  C      K. A      P F C  L U 

    G C  P F C    . F    x  F C,       x  ,  a  L U ,  ⟨a x x⟩ ,  i ∥x ∥  ⟨  ⟩          ∥∥ F , i   () q       L U  F  C  F  C    .   xa 

Proposition 1.7. — Wih he noaions inroduced above, he poin x  P F C is minimal i and only i he linear map   x is idenically zero.

F         P 1.2  C 3     . 1.5. Lowest height on the quotient. — S   ∥∥ MD        MD      Y    . S   h   X L G   h M Q Q  Y Q 

B   h   X L G      C   F  F      .

Corollary 1.8. — Le P  X K be a semi-sable K-poin. Ten he insabiliy measures v P are almos all zero and ∑    h L P  v P  h   X L G  K  Q v V K

F                q. 1.6. Te lower bound o Bost, Gasbarri and Zhang. — L N         e       e N   . C  oK  

G  GLeoK oK    oK GLe N oK  S  SLeoK oK    oK SLe N oK 

      K  C      U  Ue        Ue N   G C

SU  SUe        SUe N   S C

L F       oK     G  GL F   ,      oK  ,     :         K  C   ∥∥ F           U . B     1.4.

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L E   E      EN    N       oK    Ei  ei   i       N .           F E   F  “”   E ( S 3.1    ). T    F E     ,  E  GE  GL E  oK    oK GL EN   GL FE

    . C:

SE  SL E  oK    oK SL EN  XE  P FE L E  OFE     FS    F E  YE   q  XE    SE  LE T       homogeneous o weigh a  a       a N   ZN ,   oK  T    t       t N  Gm T , t    E      t N   EN   t a    t Na N   F 

heorem 1.9 (c. T 3.8). — Wih he noaions inroduced above, i he represenaion  is homogeneous o weigh a  a       a N   ZN and he subse o semi-sable poins X is no empy, hen: 1) here exiss an isomorphism  E  YE  Y; 2) or every D   divisible enough here exiss a canonical isomorphism o hermiian line bundles, ha is an isomeric isomorphism o line bundles,  E  M D E   E M D 

N ⊗ i 

f E  Ei ai D ei 

where f E  YE  S oK is he srucural morphism; N     ∑ 3) h   XE LESE  h   X LS  ai    Ei . i 

Corollary 1.10. — Wih he noaion o Teorem 3.8, or every K-poin P o XE which is semi-sable under he acion o SE: h L P   E

N ∑ i 

  ai    Ei   h   X LS 

F N         G [32, T 1]         B [12, P 2.1]  Z [75, P 4.2]. 1.7. An explicit lower bound. — I ,               q. L N         E   E      EN  MÉMOIRES DE LA SMF 152

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  N       oK   . C   oK  

G  GL E  oK    oK GL EN  S  SL E  oK    oK SL EN 

       K  C     , U  U∥∥ E       U∥∥ EN    G C

SU  SU∥∥ E       SU∥∥ EN    S C

L F       oK     G  GL F         ,  ,      K  C   ∥∥ F           U . C     S  F. B      1.4. F    n    n  n ∑  i   ℓn  n n i 

T ℓn   n ,  S’ , ℓn   n  n  .

heorem 1.11 (c. T 4.1). — Wih he noaions inroduced above, le N ] ⊗ ϕ E Ei  ai oK Eibi  F i 

be a G-equivarian and generically surjecive homomorphism o hermiian vecor bundles. Ten, N ∑ ∑    h  P F OFS   bi    Ei    bi ℓ Ei  i  Ei  

i 

wih equaliy i b      b N  .

A,        : Conjecture 1.12. — Under he same hypoheses o Teorem 1.11,

N ∑   bi    Ei  h  P F OFS   i 

T     T 1.11                         oK . T      [22]  [16].

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2. Examples o height on the quotient 2.1. Endomorphisms o a vector space 2.1.1. Semi-sable endomorphisms. — L k       E   k    ()  n. C        k GLE   f k X  EE  SA  A  Sk EE . F   ϕ  E  E   Pϕ T    , Pϕ T   T  E ϕ  T n   ϕT n      n n ϕ

T f  ϕ     n ϕ     f  ϕ, i.e.   A,        SLE. Proposition 2.1 ( [49, P 2]). — Te afne space Ank ogeher wih he map     EE  Ank  ϕ   ϕ     n ϕ 

is he caegorical quoien o X by SLE. In paricular, he invarians       n generae he k-algebra o invarians ASLE  . Proposition 2.2 ( [49, P 4]). — Le ϕ  E  E be a linear map. Ten:

1) he orbi o ϕ is closed i and only i ϕ is semi-simple i.e. i can be diagonalized; 2) he closure G  ϕ o he orbi o ϕ conains he orbi o he semi-simple par ϕ  o ϕ.

Corollary 2.3. — For every non-zero endomorphism ϕ  E  E he associaed k-poin ϕ  PEE is semi-sable i and only i ϕ is no nilpoen. 2.1.2. Arihmeic siuaion. — L K      oK     . L E       oK . C      S  SL E  E E. E  oK  E E      ( § 3   9). T  ∥∥ E E           SU∥∥ E   G C. B    1.4 ( F  E E  G  S). heorem 2.4. — Wih he noaions inroduced above, le ϕ be an endomorphism o he Kvecor space E oK K. Suppose ha he corresponding K-poin ϕ o PE E is semi-sable ha is, he endomorphism ϕ is no nilpoen. Ten, Ω  Qh M  ϕ is equal o  ∑ ∑       v      n v           n   v VΩ .

  ΩC

where        n are he eigenvalues o ϕ couned wih mulipliciies and Ω is a number eld conaining hem.

MÉMOIRES DE LA SMF 152

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T  q Y      PE E  SL E         Sn   ( ,     q  Pon K   P      n  oK ).  C  “” A  h  Pon , i.e.   ,    K  Ω  K   Ω          n ,   ∑ ∑         v      n v           n   Ω  Q v V Ω  Q   ΩC Ω

.

T,        h M    h  Y    q Pon  Y  Sn . K T           T 2.4.

2.1.3. Reducion o local saemens. — L v     K   E   Cv     n. L e       en     E  q E    ∥∥E       x  v      x n v  ∥x e       x n en ∥E     x  v      x n v 

 v    v  

Eq  Cv   EE    ∥∥ EE   : ∥ϕ ∥ EE 

  ∥ϕx∥E ∥x ∥E     x ,      ∥ϕe  ∥E      ∥ϕen ∥E 

 v    v  

I      ∥∥E      o E  o  e       o  en  E ( o       Cv ). T  ∥∥ EE       o EE  EE. I    ∥ϕ ∥E  ϕ  ◦ ϕ  ϕ       ϕ       ∥∥E . Proposition 2.5. — Wih he noaion inroduced above, or every endomorphism ϕ o E, 

д SLECv 



∥дϕд ∥ EE 

      v      n v        v      n v 

 v    v  

where        n are he eigenvalues o ϕ (couned wih mulipliciies). Proo o Teorem 2.4. — I f    F F      C 1.6           P 2.5. □

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CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

I    P 2.5,  f          (     e       en ),

 .

          n       

   

   

      

    n 

2.1.4. Compuing minimal endomorphisms. — I            ∥ϕ ∥ EE    ∥дϕд ∥ EE   д SLECv 

Proposition 2.6. — Le        n  Cv . Wih he noaions inroduced above, he endomorphism ϕ         n  is minimal. Proo o Proposiion 2.6: he non-archimedean case. — L v     . P 1.42) f     ϕ         ϕ    F v   PEE o F p . L        n    Cv        . U     ϕ         n        v      n v  

T     ϕ   F p   PEE     ϕ        n    F p   E o F p  F p  e       F p  en 

,   i       n, i  F p     i . T  ϕ    ,  . T,   P 1.43),   ϕ  ,        . □ Proo o Proposiion 2.6: he archimedean case. — L suE   L    L  SU∥∥E . A     X C  suE        :     ϕ            A  suE     ϕ  A 

 ⟨A ϕ ϕ⟩ EE  , i ∥ϕ ∥ EE 

 A ϕ  Aϕ  ϕA   L  , ⟨  ⟩ EE         ∥∥ EE   i   q   .  A  P 1.7,   ϕ       ϕ A    A  suE. T  q    : ⟨Aϕ ϕ⟩ EE   ⟨ϕA ϕ⟩ EE 

  A  EE

Lemma 2.7. — Wih he noaion inroduced above, or every endomorphism ϕ o E he ollowing condiions are equivalen:

MÉMOIRES DE LA SMF 152

2. EXAMPLES OF HEIGH ON HE UOIEN

123

1) ⟨Aϕ ϕ⟩ EE   ⟨ϕA ϕ⟩ EE  or all A  EE; 2) ϕ ϕ  ϕϕ  , where ϕ  denoes he adjon endomorphism o ϕ wih respec o he norm ∥∥ EE  ; 3) Te endomorphism ϕ is diagonalisable on a orhonormal basis. Proo o Lemma 2.7. — T q  2)  3)       . T    q  1)  2)     . F  i j       n  Ai j    E   Ai j ek    ik e j   k       n  (  ik  K’ ). W ϕ  ni j  ϕ i j Ai j . W  ,   i j       n, n n ∑ ∑ ϕ jk Aik  ϕAi j  ϕ ki Ak j  Ai j ϕ  k 

k 

T  Ai j      EE ,  i j       n, ⟨Ai j ϕ ϕ⟩ 

n ∑

k 

O   ,  , ϕ  ϕϕ  

n ∑

i j 

⟨ϕAi j  ϕ⟩ 

ϕ jk ϕ ik  n

i j  ϕ ji Ai j .

ϕ ki ϕ k j 

k 

T

ϕ ϕ 

⟨Ai j ϕ ϕ⟩Ai j 

n ∑

n ∑

i j 

⟨ϕAi j  ϕ⟩Ai j 

I             q.



T  L   :            n  □    ϕ         n   . 2.1.5. A varian. — L      .  ∥∥ EE   EE    : ∥ϕ ∥    x ,

I       SU∥∥E .

I   

∥ϕx∥E  ∥x ∥E

Proposition 2.8. — Wih he noaion inroduced above,    ∥дϕд ∥           n  д SLEC

where        n  C are he eigenvalues o ϕ couned wih mulipliciies

Proo. — F  i       n  vi         i :   д  SLE C   i       n,   дϕд д  vi   i   ∥д  vi ∥E  E

I ,   д  SLE C,

  ∥дϕд ∥           n 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

124





д SLEC

  ∥дϕд ∥           n  

S          n        SLE  ϕ,      ∥дϕд ∥           n           n   

д SLEC

   .



T        ,       P 2.5. 2.2. Te lowest height on the orbit is not the height on the quotient 2.2.1. Te quesion. — L         S 1.1   P    K  X. S     G: (2.1)

 h L д  P 

д  G Q 



 P ′  P 

h L P ′

            Q  X       P. S    v P        v  VK ,  F F  h L P  h M  P, :   (2.2)  h L P ′  h M  P  ′  P  P 

C   q: (2.3)

   h L д  P  h M  P 

д  G Q 

Qestion. — W   q (2.1), (2.2)  (2.3) ? T      G  GLnZ      F  : 1) I    ( n  )    q (2.2)  (2.3)         F    3 . 2) I    ( n   )      F        ( , F  Zr        Rr )   f. T            Gm    ,  ,   Gm  GL F   . 3) I   ,   GLnZ   F  EZn   . E F      ( § 3   9)        Rn . I        q (2.2)  (2.3)   q    Q  P F     ( P F ). N, q (2.1)    q           . 3. A    E     K          E   E.

MÉMOIRES DE LA SMF 152

2. EXAMPLES OF HEIGH ON HE UOIEN

125

2.2.2. Linear acion on a non-rivial hermiian vecor bundle. — C    Gm  AZ   t  x   x    t x   tx  

   S,  t  Gm S   x   x    A S. C     G  Gm  X  PZ   G  L  O. F   k, X k  P k   

L Y    q  X (     S Z)     X  Y  q . F   r  r   r          ∥∥r  R   ∥x   x  ∥r  r  x     r  x    

E    L   FS    ∥∥r ,        U. D  Lr      X       h Mr     q Y   Lr . Proposition 2.9. — Wih he noaions inroduced above: 1) Te poin     P Q is semi-sable and

 h Mr       r r  

2) For every t  Gm Q,

h Lr t   t   wih equaliy or t  .



r   r  

I ,    q (2.2)  (2.3)     r   r  . T                   ( P 2.10  2.13). 2.2.3. A negaive example when he hermiian vecor bundle is rivial. — C  Z  E  Z         x   x   x    x     x     x    

L Gm   Z 

t  x   x   x    t x   tx   t x  

C     Gm  X  PZ     O. E O   FS      ∥∥. Proposition 2.10. — Consider he poin P      . Wih he noaions inroduced above: 1) Te poin P is semi-sable and     h M  P       SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

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2) For every t  Gm Q,

h O t  P   

wih equaliy or t  .

T   q (2.2)  (2.3)   ,       E  . Proo. — 1) T     P  . F    p ,    P      P        P Fp 

     PFp . I           P     q    Q. O   ,  p  ,   no : ,                  PF . F  t  Gm C ,      t          t      t       t     T         t     ,        t              t Gm C 

F  F F  ∑   h M  P    v VQ

t Gm Cv 

   t            v

2) L K       t  Gm K. F    v   ,      t     v      t v    t v 

  v  ,      t     v      t v      t v 

T,      K,     P F,   K  Qh O t  P     }  ∑  { ∑   ∑       t     t     t   t       K C t    K C   K C

Lemma 2.11. — Le N   be a posiive ineger. For every x       x N  R,  

N {∑ i 

xi 

N } ∑ x i  e x i  e x i  e x i   N    i  i 

N ∑

Proo o he Lemma. — L      RN  R    x       x N    

N {∑ i 

MÉMOIRES DE LA SMF 152

xi 

N } ∑ x i  e x i  e x i  e x i   i  i 

N ∑

2. EXAMPLES OF HEIGH ON HE UOIEN

127

T           . T        R  RN ,  ,           R  R     x  N  x x    e x  e x  e x   T         . T   x  R,   .

x    N  



L        P 2.10. O           N  K  C,  N  K  Q,     L  x i   t i   i       N . T, h O д  P       . □ 2.2.4. Endomorphisms. — L n             E    Z E  Zn      . L e       en      E. A  S 2.1       G  SLnZ  F  E E        2.1.2. F    K           n  K,          n     E  K  K n     (    ),           n       

            

       n  Proposition 2.12. — Le        n  K and suppose ha hey are no all zero. Wih he noaion inroduced above,     h OF         n   h M         n  

In paricular, or all non-zero semi-simple endomorphism ϕ o K n ,      h OF  д  ϕ  h M  ϕ  д SLn Q 

T    q  T 2.4. T   q (2.2)  (2.3)      ,  ,       . H, q (2.1)    q  . F ,  n       ϕ  E     (    ), ( )   ϕ   

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

128

Proposition 2.13. — Wih he noaions inroduced above: 1) Te endomorphism ϕ is semi-sable and    h M  ϕ    

2) For every д  SL Q,

wih equaliy or д  .

   h O д  ϕ    

Proo. — 1) T    q  T 2.4. 2) L K       д  SL K      ( ) a c д  b d  a b c d  K    ad  bc  . W  , ) (   ab a   дϕд   b    ab

F    v  K:     ∥дϕд ∥ v     ab v    ab v  av  b v    av  b v 

O   ,       K  C,

  ∥дϕд ∥    ab     ab   a  b     a  b  

S a , . S b v      v  VK ,     ∑ ∑      K  Qh O д  ϕ     a     av   v VK 

  K C

T   P F: { ∑ } { } ∑ ∑      av     av      a  v VK 

v VK 

  K C

 P     ,   K  Qh O д  ϕ     { } ∑ ∑   (2.4)     a      a    K C

  K C

Lemma 2.14. — Le N   be a posiive ineger. For every x       x N  R, N } { ∑   x i  i 

 

N ∑ i 

   e x i   N   

T     L       L 2.11.

MÉMOIRES DE LA SMF 152

3. HE APPROACH OF BOS, GASBARRI AND ZHANG

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L        a , . O           N  K  C

 N  K  Q,     L  x i   ai   i       N . A  (2.4),    h O д  ϕ     T  a    b ,    . □ 3. Te approach o Bost, Gasbarri and Zhang 3.1. wisting by principal bundles. — I             B, G  Z        B ,         G. 3.1.1. Te algebraic consrucion. — L G         S. L X   S    ()   G   P    G 4 (        Z ). B ,  wis o X by P    q  X S P   ()   G   д  x p  дx pд    S S ′    д  GS ′  x p  X S ′  PS ′. C, X P    :  1) P   S  i I S i      P   ,   i  I ,  pi  S i  P   . 2) G   X S S i    X S S i j  X S S i j 

x  дi j  x

 S i j  S i  S j  дi j   q S i j   G  p j  pi . I  X P    X     S. T        : 1) L G     . T  G P   S      X P . M ,  H     G (     ,   S S ′,   H S ′      GS ′)  H P      G P . 2) L G       F  S   VF P     P     VF   F . C    S      U  S    U  F P   MS U  VF P  T F P      S,  S  G P         VF P     VF P . T   F P     F  P. 4. A principal G-bundle P   S     ()    P S G  P  : 1)       P S G  P S P     S ;  2) P      Z :      S  i I S i    i  I     pi  S i  P .

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CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

3) L L   G    X   VLP    P     VL  X . C   L P    X P  X  P      U  X P    U  L P   MS U  VLP T L P  G P     X P     VL P   X P    VLP .

Example 3.1. — L N        e       e N   . C    S : G  GLeS S    S GLe N S  S  SLeS S    S SLe N S 

L E  E       E N    N      S   Ei    ei   i.  E     G P E  FS E   S    S FS E N 

   i  S FS Ei    rame bundle  Ei :   S f  S ′  S, FS Ei S ′  I OS ′  OSei′  f  Ei 

T ()   G  P E       . L       F  S      G  GLF . C     G  X  PF      L  OF . D  F E    F  P E . T: G E  GLE   S    S GLE N  S E  SLE   S    S SLE N 

X E  PF E 

L E  OF E     G E , S E , X E  L E   G P E , S P E , X P E  L P E . 3.1.2. Te hermiian consrucion. — L      . L G       CG  GC    . D   G CG   G. Deinition 3.2. — A principal hermiian G-bundle    P C P      G       C P  PC         G,   .

C P  CG  C P  C P 

p u  p pu

L X  X  C X                 C X  X C. S  G   X        CG  C X . MÉMOIRES DE LA SMF 152

3. HE APPROACH OF BOS, GASBARRI AND ZHANG

131

Deinition 3.3. — L P  P C P      G. T wis o X by P    X P  X P  C X P ,  X P     X  P  C X P         C X  C P CG  X P C  X C  PC GC

N           G.

L p  C P       x  X C   x p    x p  X P C  X C  PCGC. T   X C  X P C

x  x p

       C X  C X P . L P    P . T      G        : 1) L G     . T   G  G CG   P    G P  CG P        G P      CG P  G P C. L H  H  C H           H  G      C H  H C       CG . T H P     H P  C H P       H P  P (       G P )       H P C. 2) L F  F  ∥∥F    ( )   . S  G    F     ∥∥F       CG . C   VF   VF  DF     DF  v  F  ∥v ∥F    L VF  P  VF P  DF P      VF   P . T    q   ∥∥F P  F P     DF P  v  F P  ∥v ∥F P   

T    F P  F P  ∥∥F P      F  P . 3) L X           G    G    L. S  L  q     ∥∥L        CG . C   VL  VL DL   VL      L  X    DL  x s  x  X C s  x  L ∥s ∥L x    R  X C  ,  DL      VLC. M        CG . L   VL P  VL P  DL P      VL  P . T   q   ∥∥L P  L P     DL P  x s  x  X P C s  x  L P  ∥s ∥L P x  

T    L P  L P  ∥∥L P      L  L ∥∥L   P .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

132

Example 3.4. — L N         e       e N   . C     G  GLeC C    C GLe N C 

S  SLeC C    C SLe N C 

    

CG  U  Ue        Ue N 

C S  SU  SUe        SUe N 

L E  E       E N    N     ,      E i  Ei  ∥∥Ei

      Ei     ∥∥Ei . S C Ei  ei   i.    E      G P E  P E  C E    P E  FC E   C    C FC E N 

C E  OE        OE N 

,   i, FC Ei       Ei  OE i    orhonormal rame bundle  E i , i.e.      Cei  E i ( Cei       ). L F  F  ∥∥F          G  GLF   . S    ∥∥F       U. C     G  X  PF      L  OF     FS  ∥∥L . D  F E  F E  ∥∥F E     F  P E . T: 1)      G U  P E    G E  U E   G E  GLE   S    S GLE N 

U E  U∥∥E       U∥∥E N  

2)      S SU  P E    S E  SU E   S E  SLE   S    S SLE N 

SU E  SU∥∥E       SU∥∥E N  

3)        L  L ∥∥L   P E      L E  L E  ∥∥L E   X E  PF E   L E  OF E 

∥∥L E  FS    ∥∥F E 

3.2. Statement and proo o the result 3.2.1. Seup. — L K    . L N         e       e N   . C  oK  

G  GLeoK oK    oK GLe N oK 

S  SLeoK oK    oK SLe N oK 

      K  C      U  Ue        Ue N   G C

SU  SUe        SUe N   S C

L F       oK     G  GL F   ,      oK  ,     :         K  C   ∥∥ F           U .

MÉMOIRES DE LA SMF 152

3. HE APPROACH OF BOS, GASBARRI AND ZHANG

133

T    G  F     G  X  P F   G  L  O. F     K  C     O X C   FS ,       U      . C       X     S     q Y  XS  X  S,  Y  P AS    A  X Ld   SodK  F  d 

d 

L   X  Y  q . F   D      MD       Y   LD . E        S 1.1. S S    G,   d  ,  oK   S    Ld ,  X Ld S   X Ld 

       G   X Ld . T         X       G. M G    q Y ,   D    ,    MD  G. F     K  C   ∥∥ MD        U . 3.2.2. wising by hermiian vecor bundles. — L E   E      EN    N        oK    Ei  ei   i       N . A      S 3.1.1       N   oK  E   E   EN        E. G       E 3.1,  FE GE, SE, XE, LE     F, G, S, X, L  E. T:

GE  GL E  oK    oK GL EN  XE  P FE

SE  SL E  oK    oK SL EN  LE  OFE 

T oK   GE    FE     LE  GE      X   G . C    XE E E   S ,     LE. D  XESE   q  XE E  D    ,  MD E       LED . Proposition 3.5 (C  GI q  ). — Wih he noaions inroduced above:  is he wis o X by E; 1) Te se o semi-sable poins XE 2) Te quoien XESE is he wis o he quoien Y  XS by E; 3) Te inverible shea MD E is he wis o MD by E. Skech o he proo. — A       . Remark 3.6. — L V      oK       G. D  VE    E. T   VESE     VE  SE      VS E  VS  E.

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

134

T  : ,        VS E  VESE   q       S oK .       P  f       □ V   X Ld    d  .

L   K  C    . B ,     ,    G C  GL FC

   ,  ,   ∥∥ F       U . T        S 3.1.2. G        E 3.4,     FE  C       ∥∥ FE                U E  U ∥∥ E      U ∥∥ EN   T   LE     FS  ∥∥ LE     ∥∥ FE . T  ∥∥ LE            SU E  SU ∥∥ E      SU ∥∥ EN   S C

L ∥∥ MD  E         MD   S 1.1. T  ∥∥ MD   MD       U :  ∥∥ ′MD  E  

  MD E        M D  E.

Proposition 3.7. — Wih he noaions inroduced above, he merics ∥∥ MD  E , ∥∥ ′MD  E coincide. Proo. — T     i  Cei  Ei  C   i       N . T      . □ 3.2.3. Saemen. — K    . B       homogeneous o weigh a  a       a N   ZN    oK  T    t       t N  Gm T ,   t    E      t N   EN   t a    t Na N   F  heorem 3.8. — Wih he noaions inroduced above, le E   E      EN  be a N -uple o hermiian vecor bundles over oK such ha  Ei  ei or every i. I he represenaion  is homogeneous o weigh a  a       a N   ZN and he subse o semi-sable poins X is no empy, hen: 1) here exiss an isomorphism  E  YE  Y; 2) or every D   divisible enough here exiss an isomorphism o hermiian line bundles, ha is an isomeric isomorphism o line bundles,   E  M D E   E M D 

N ⊗ i 

f E  Ei ai D i ei 

where f E  YE  S oK is he srucural morphism; N ∑ 3) h   XE LESE  h   X LS  ai    Ei . i 

MÉMOIRES DE LA SMF 152

3. HE APPROACH OF BOS, GASBARRI AND ZHANG

135

Corollary 3.9. — Wih he noaion o Teorem 3.8, or every K-poin P o XE which is semisable under he acion o SE, h L P   E

N ∑ i 

  ai    Ei   h   X LS 

3.2.4. Proo o Teorem 3.8. — L           . Proposition 3.10. — Le V be non-zero oK -module which is a and o nie ype. Le r  G  GL V be a homogeneous represenaion o weigh b  b      b N . I he submodule VS o S-invarian elemens o V is non-zero, hen: 1) ei divides bi or every i       N ; 2) he induced represenaion r  G  GL VS is given by r д      дN  

N ∏

 дi bi ei

i 

or every oK -scheme T and or every д      дN   GT . Proo. — C    r  G  GL VS. S    S  FS    ,   r      oK   N  GL VS r   GS  Gm

T  r     b  b      b N , ,   oK   T   t       t N  Gm T , O   , 

bN    r t    E      t N   E   t b    t N

r t    E      t N   E   rt e      t Ne N  bN rt e      t Ne N   t b    t N   

S 1)  2)   .



Corollary 3.11. — Under he hypoheses o Teorem 3.8:  Te acion o G on Y is rivial;  For every ineger D   divisible enough he oK -group scheme G acs on he bres o MD hrough he characer N ∏ д      дN    дi ai D ei  i 

More precisely, or every oK -scheme T , every д      дN   GT , every poin y  YT  and every secion s  T  y  MD , N  ∏  д      дN   y s  y  дi ai D ei  s  i 

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

136

Proo. — P D   MD   . T,      O ≃ M  Gq. T j D  Y  P Y MD      j D D    Y MD      S  X LD S  SoDK  F  

S        a  a       a N ,     SoDK  F      Da  Da       Da N 

I   P 3.102)   V  SoDK  F      G   Y MD       N ∏ д      дN    дi ai D ei    i 

A 1)  2)   .



T 3.8     C: Proo o Teorem 3.8. — A  P 3.52),  q YE      q Y  E:  G   ,       E  YE  Y

S,   P 3.53)  P 3.7,      M D E        M D  E. S    G     MD      N ∏  дi ai D ei  д      дN   i 

           E  M D E   E M D 

   .

N ⊗

f   Ei ai D i ei 

i 



4. Lower bound o the height on the quotient 4.1. Statement. — I     T 1.11. L         1.5. L N         E   E      EN    N       oK   . C   oK  

G  GL E  oK    oK GL EN 

S  SL E  oK    oK SL EN 

       K  C     , U  U∥∥ E       U∥∥ EN    G C

SU  SU∥∥ E       SU∥∥ EN    S C

MÉMOIRES DE LA SMF 152

4. LOWER BOUND OF HE HEIGH ON HE UOIEN

137

L F       oK     G  GL F         ,  ,      K  C   ∥∥ F           U . C     S  F      1.4.

heorem 4.1. — Le a  a       a N  and b  b      b N  be N -uples o inegers. Wih he noaions inroduced above, le ϕ

N ⊗  i 

 E Ei  ai  Eibi  F

be a G-equivarian and generically surjecive homomorphism o hermiian vecor bundles. Ten, N ∑ ∑      Ei   h  P F OFS   bi   bi ℓ Ei  i 

wih equaliy i b      b N  .

i  Ei  

T  ϕ  Gq     v     v  K (    ,     ϕ       oK ). F  ,  f   T 4.1    ϕ  ,  : heorem 4.2. — Le a  a       a N  and b  b      b N  be N -uples o inegers and se

F 

N ⊗  i 

Wih he noaions inroduced above,

 E Ei  ai  Eibi 

N ∑   bi    Ei   h  P F OFS   i 

wih equaliy i b      b N  .



i  Ei  

  bi ℓ

Ei 

T   S 4       T 4.2. 4.2. ensor products o endomorphisms algebras 4.2.1. Noaion. — I        T 4.2    bi     i       N ,  ,    N ⊗ F E Eiai  i 

  N    a  a       a N .

heorem 4.3. — Wih he noaion inroduced above,   h  P F OS   B    q:

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

138

Proposition 4.4. — Wih he noaion inroduced above,   h  P F OS  

Proo. — T     E Eiai  ≃ E Eiai    ai    . A  T 3.8  f     K  Q      Ei  ,  ,   i       N ,     Ei   Z Ei  Zei      . C     E′  Ea      ENa N . I         E′  Za e  a N e N      . W       Sq      F ≃ E E′. C   ϕ  E′     (      E′)           :    ϕ      

   

   

     

    

T  ϕ  P F         SL E′ (       S)     . I h M      q Y  P F  S    P F  Y   q ,  F F    (C 1.6)      h M  ϕ  h OF  ϕ      .



I      q. I f  : heorem 4.5. — Le ϕ  F oK K be a non-zero vecor such ha he associaed K-poin ϕ o P F is semi-sable. Ten, ∑ ∥д  ϕ ∥ Fv     д SCv  ∥ϕ ∥ Fv v V K

I, T 4.3    T 4.5   F F (     C 1.6)     K ′  K       P F   K ′. T           T 4.5. 4.2.2. Te case o a non-nilpoen endomorphism. — C ϕ      N a i K  oK K      i  Ei 

N ⊗ i 

MÉMOIRES DE LA SMF 152

E Eiai  ≃ E

N ⊗ i 

 Eiai 

4. LOWER BOUND OF HE HEIGH ON HE UOIEN

139

W     ϕ   . T   ϕ      S. A,    :   oK  

H  SL Ea      ENa N 

      F(    ). A  C 2.3,   ϕ       H. T ϕ      S ,    v  K, (4.1)



д SCv 

∥д  ϕ ∥ Fv 



h  HCv 

∥hϕh  ∥ Fv 

T          F         N N N  ⊗  ⊗  ⊗ Eiai  Eiai oK Eiai  E i 

i 

i 

T    T 2.4  ϕ      ∑   ∥hϕh  ∥ Fv Ω  K

 q 

v VK



v VΩ .

h  HCv 

      v      n v 



  ΩC





        n  

        n     ϕ (  )  Ω      . S   q  ,     (4.1)   , ∑ ∑   ∥д  ϕ ∥ Fv    ∥hϕh  ∥ Fv   v VK

д SCv 

  T 4.5   .

v VK

h  HCv 

4.2.3. Te case o a non-vanishing invarian linear orm. — S     S    f  P F O  F      ϕ.                  F M T  I T. T      . F  i       N  S ai       ai  . F      i     Eiai     . S     E Eiai ,   i      SL Eai . T ,   N   ,          N   S a       S a N 

             N  N  F       S.

W     F M T  I T (c. [71, C III], [22, T 3.1, C]  [2, A 1]):

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

140

heorem 4.6 (F M T  I T). — Te subspace o elemens o F oK K which are invarian under he acion o S oK K is generaed, as a K-linear space, by he elemens   , while  ranges in S a       S a N  .

F  N             N   S a       S a N           

F

N ⊗ i 

E Eiai  ≃ F 

N ⊗ i 

E Eiai 

L      T 4.5. S    S      ϕ,   T 4.6,     N             N   S a       S a N      ϕ , . B ,   ϕ  ϕ ◦    

S      ϕ ◦         . T,    : ∑   (4.2)   д  ϕ ◦       Fv

д SCv 

v VK

R   : 1) F   v  K       F oK Cv , ∥ ◦    ∥ Fv  ∥ ∥ Fv 

2) T          S (     S ). A  q   ,   д  SCv ,   ∥д  ϕ ∥ Fv  д  ϕ ◦      Fv

S   ,   q   (4.2)  ∑   ∥д  ϕ ∥ Fv   v VK ′

д SCv 

  T 4.5   .

4.2.4. Te general case. — L      . B          D     S     f   P F OD  SD  F 

       ϕ. C  D V  P F  P FD 

ϕ  ϕ D 

T  ϕ D       P FD . S FD  SD  F        Sq ,     P         , f         S  f ′  FD oK K. 5 5. L k      V  W      k  G. A Gq  ϕ  V  W    ϕ  V G  W G . I ϕ    k        V G  W G   [49,  181–182].

MÉMOIRES DE LA SMF 152

4. LOWER BOUND OF HE HEIGH ON HE UOIEN

141

U   f ′        S     f ′   P FD  O

     ϕ D . T        ϕ D   ∑   ∥д  ϕ D ∥ FD v   д SCv 

v VK

F   v  K    д  SCv , D  ∥д  ϕ D ∥ FD v  ∥д  ϕ ∥ Fv 

     T 4.5.



4.3. Te general case 4.3.1. Noaion. — I          T 4.2. A  T 4.3      : heorem 4.7. — Le ϕ  FoK K be a non-zero vecor such ha he associaed K-poin P  x o P F is semi-sable. Ten, ∑ ∥д  x ∥ Fv     д SCv  ∥x ∥ Fv v V K

T           T 4.7.

4.3.2. Te case o a non-vanishing invarian linear orm. — S     S           P. I ,    S   N ⊗   F  E Ei ai  Eibi i 

 . T P 3.101)   ei   Ei  bi  i       N . T      P F   T 4.7     T  4.3. Deinition 4.8. — F   i       N . 1) F ei  ,  i    oK  i  Ei  E Ei    Ei

   ,   ϕ  E Ei   v   v   Ei ,    ϕ  v   v    ϕv    v   ϕv    v  

2) F ei , ,  i     oK    ,

i  Eiei  E Eiei    Ei  i  E Eiei    Ei  Eiei  SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

142

   :   ϕ  E Eiei    v       vei  Ei ,      ϕ  v       vei   ∑  ϕv       v ei    v       vei   Sei

E  oK  E Ei    Ei  E Eiei    Ei      (   ,    )     ∥∥ Ei . Proposition 4.9. — Fix an ineger i       N . Wih he noaions inroduced above:  or ei  , i is a GL Ei -equivarian isomorphism o hermiian vecor bundles;  or ei , , i is GL Ei -equivarian and, or an embedding   K  C,  x ,

 ∥i x∥  ei   ∥x ∥

where he supremum is ranging on he elemens o Eiei  C, he norm in he numeraor is he one o E Eiei    Ei and he norm in he denominaor is he one o Eiei . Proo. — T     i  GL Ei q     . L   K  C       W  Ei  C

w  C W  ei 

∥∥W  ∥∥ Ei  

f  i 

L x       xw      W . 1) I w      ϕ  W :       f ϕ  x   x     ϕx    x   ϕx    x    W W     ∥ϕx  ∥W  ∥ϕx  ∥W    ∥ϕ ∥ EW   ϕ  x   x   EW   W 

   f  ( f )   . 2) S w , . F  w R  r       rw     r        w  (       w)  x R  x r       x rw 

W R          w w   x R         W w . F   t  W w  ∑ tR xR  t R   w w

L x       xw     W    x       xw       Sw  x  x       x w  . W  ,   t  W w ,   f    ∑ ∑ f t   t R x R  x  x       xw  R   w w  Sw

MÉMOIRES DE LA SMF 152

4. LOWER BOUND OF HE HEIGH ON HE UOIEN

     :    f t  EW w  W



R   w w

 t R    w  ∥t ∥W w 

b e i

F  i       N   i i b i E ≃  Eei  bi ei ,   : bi 

ei  

i

ei , 

i

bi e i

143



,   

 Eibi  E Ei  bi    Ei  bi    Eibi  E Ei  bi   Ei  bi ei 

F  i       N   oK   E Ei  ai bi  ′ Fi  E Ei  ai bi

 ei   

    oK  bi e i

i   i

bi e i

 E Ei  ai  Eibi  Fi′   Ei



S     T            N      Gq   oK    F  F′  D, 

F′

F′

FN′ .

D 

N ⊗ i 

bi e i

 Ei



E F′  D           Ei . P    ,     Gq     P F  P F′  D

T,    P         (  5),    P    K  P F′  D       S. I x  F oK K      P,  F F    (C  1.6)  P 4.9 : ∑ ∥д  x ∥ Fv   h M  P  д SCv  ∥x ∥ Fv v V ∑

K



v VK





д SCv 

∑ bi  ∥д  x∥ F′  Dv  ℓei   ∥x∥ F Dv i e   i

S    S       D,      P F′  D  P F′

 Sq. M,         

  OF′  ≃ OF′  D  f  D 

 f  P F′  S oK    .

SOCIÉÉ MAHÉMAIUE DE FRANCE 2017

CHAPER 4. HEIGHS ON GI UOIENS: FURHER RESULS

144

L Y′   q  P F  S    ′  P F′  Y′   q  . D  h M′      q Y′ (   S  OF′ ). A   F F,   ∑



v VK



д SCv 

  ∑ ∥д  x∥ F′  Dv  h M′  ′ ◦ P  bi    Ei  ∥x∥ F Dv i  N

 ,   ,  

N ∑ bi   ∑    bi    Ei   h M  P  h M′  ′ ◦ P  ℓei   i e   i  i

T  T 4.3   h M′  ,      T  4.7   . 4.3.3. Te general case. — S     S     s   P F OD

     P. O     4.2.4 — ,   D  P F  P FD      . T      . T      T 4.7,   T 4.2. □

MÉMOIRES DE LA SMF 152

BIBLIOGRAPHY

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MÉMOIRES DE LA SOCIÉTÉ MATHÉMATIQUE DE FRANCE Nouvelle série

2017 152. M. MACULAN – Diophanine applicaions o geomeric invarian heory 151. T. SCHOENEBERG – Semisimple Lie Algebras and heir classiicaion over p-adic Fields 150. P.G. LEFLOCH , YUE MA – The Mahemaical Validiy o he f R Theory o Modiied Graviy 2016 149. BEUZART-PLESSIS R. – La conjecure locale de Gross-Prasad pour les représenaions empérées des groupes uniaires 148. MOKHTAR-KHARROUBI M. – Compacness properies o perurbed sub-sochasic C  -semigroups on L   wih applicaions o discreeness and specral gaps 147. CHITOUR Y., KOKKONEN P. – Rolling o maniolds and conrollabiliy in dimension hree 146. KARALIOLIOS, N. – Global aspecs o he reducibiliy o quasiperiodic cocycles in compac Lie groups 145. V. BONNAILLIE-NOËL, M. DAUGE, N. – Ground sae energy o he magneic Laplacian on corner domains 144. P. AUSCHER, S. STAHLHUT – A priori esimaes or boundary value ellipic problems via irs order sysems & A priori esimaes or boundary value ellipic problems via irs order sysems 2015 143. R. DANCHIN, P.B. MUCHA – Criical uncional ramework and maximal regulariy in acion on sysems o incompressible lows 142. Joseph AYOUB – Mois des variéés analyiques rigides 140/141. Yong LU, Benjamin TEXIER – A Sabiliy Crierion or High-Frequency Oscillaions 2014 138/139. Takuro MOCHIZUKI – Holonomic D-Modules wih Beti Srucures 137. Paul SEIDEL – Absrac Analogues o Flux as Symplecic Invarians 136. Johannes SJÖSTRAND – Weyl law or semi-classical resonances wih randomly perurbed poenials 2013 135. L. PRELLI – Microlocalizaion o subanalyic sheaves 134. P. BERGER – Persisence o Sraiicaion o Normally Expanded Laminaions 133. L. DESIDERI – Problème de Plaeau, équaions uchsiennes e problème de Riemann Hilber 132. X. BRESSAUD, N. FOURNIER – One Dimensional General Fores Fire Processes 2012 130-131. Y. NAKKAJIMA – Weigh ilraion and slope ilraion on he rigid cohomology o a variey in characerisic p  129. W. A STEINMETZ-ZIKESCH – Algèbres de Lie de dimension ininie e héorie de la descene 128. D. DOLGOPYAT – Repulsion rom resonances 2011 127. B. LE STUM – The overconvergen sie 125126. J. BERTIN, M. ROMAGNY – Champs de Hurwiz 124. G. HENNIART, B. LEMAIRE – Changemen de base e inducion auomorphe pour GLn en caracérisique non nulle 2010 123. C.-H. HSIAO – Projecions in several complex variables 122. H. DE THÉLIN, G. VIGNY – Enropy o meromorphic maps and dynamics o biraional maps 121. M. REES – A Fundamenal Domain or V 120. H. CHEN – Convergence des polygones de Harder-Narasimhan

2009 119. B. DEMANGE – Uncerainy principles associaed o non-degenerae quadraic orms 118. A. SIEGEL, J. M. THUSWALDNER – Topological properies o Rauzy racals 117. D. HÄFNER – Creaion o ermions by roaing charged black holes 116. P. BOYER – Faisceaux pervers des cycles évanescens des variéés de Drineld e groupes de cohomologie du modèle de Deligne-Carayol 2008 115. R. ZHAO, K. ZHU – Theory o Bergman Spaces in he Uni Ball o Cn 114. M. ENOCK – Measured quanum groupoids in acion 113. J. FASEL – Groupes de Chow orienés 112. O. BRINON – Représenaions p-adiques crisallines e de de Rham dans le cas relai 2007 111. A. DJAMENT – Fonceurs en grassmanniennes, ilraion de Krull e cohomologie des onceurs 110. S. SZABÓ – Nahm ransorm or inegrable connecions on he Riemann sphere 109. F. LESIEUR – Measured quanum groupoids 108. J. GASQUI, H. GOLDSCHMIDT – Ininiesimal isospecral deormaions o he Grassmannian o 3-planes in R 2006 107. I. GALLAGHER, L. SAINT-RAYMOND – Mahemaical sudy o he beaplane model: Equaorial waves and convergence resuls 106. N. BERGERON – Propriéés de Leschez auomorphes pour les groupes uniaires e orhogonaux 105. B. HELFFER, F. NIER – Qaniaive analysis o measabiliy in reversible difusion processes via a Witen complex approach: he case wih boundary 104. A. FEDOTOV, F. KLOPP – Weakly resonan unneling ineracions or adiabaic quasi-periodic Schrödinger operaors

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This text consists o two parts. In the frst one we present a proo o ThueSiegel-Roth’s Theorem (and its more recent variants, such as those o Lang or number felds and that “with moving targets” o Vojta) as an application o Geometric Invariant Theory (GIT). Roth’s Theorem is deduced rom a general ormula comparing the height o a semi-stable point and the height o its projection on the GIT quotient. In this setting, the role o the zero estimates appearing in the classical proo is played by the geometric semi-stability o the point to which we apply the ormula. In the second part we study heights on GIT quotients. We generalise Burnol’s construction o the height and refne diverse lower bounds o the height o semi-stable points established to Bost, Zhang, Gasbarri and Chen. The proo o Burnol’s ormula is based on a non-archimedean version o KempNess theory (in the ramework o Berkovich analytic spaces) which completes the ormer work o Burnol. Ce texte est constitué de deux parties. Dans la première nous présentons une preuve du théorème de Thue-Siegel-Roth (et des variantes plus récentes, comme celle de Lang pour le corps de nombres et celle with moving targets de Vojta) basée sur la théorie géométrique des invariants (GIT). Le théorème de Roth est déduit d’une ormule reliant la hauteur d’un point semi-stable et la hauteur de sa projection dans le quotient GIT. Dans ce cadre, le rôle du « lemme des zéros » présent dans la preuve classique est joué par la semistabilité géométrique du point auquel on applique la ormule. Dans la deuxième partie nous étudions la hauteur sur les quotients GIT. Nous généralisons la construction de Burnol de cette hauteur et nous améliorons plusieurs minorations de la hauteur de point semi-stables précédemment établies par Bost, Zhang Gasbarri et Chen. La preuve de la ormule de Burnol porte sur une version non-archimédienne de la théorie de Kemp-Ness (dans le langage de la géométrie analytique de Berkovich), qui complète le travail antérieur de Burnol.