English

L'espace ad\'elique d'un tore sur un corps de fonctions

Algebraic Geometry 2018-02-07 v2 Number Theory

Abstract

Let kk be a field of characteristic 0 and let KK be the function field of a smooth projective geometrically integral kk-curve XX. Let TT be a KK-torus. In this article, we aim at studying the space of adelic points T(S,AK)T(S,\mathbb{A}_K) of TT outside a finite set SS of closed points of XX. We start by proving that the group T(K)T(K) of rational points of TT is always discrete (hence closed) in T(S,AK)T(S,\mathbb{A}_K). We then describe the quotient T(,AK)/T(K)T(\emptyset,\mathbb{A}_K)/T(K) in each of the following three cases: kk is an algebraically closed field, kk is the field of Laurent series C((t))\mathbb{C}((t)), and kk is a pp-adic field. Soient kk un corps de caract\'eristique 0 et KK le corps des fonctions d'une kk-courbe projective lisse g\'eom\'etriquement int\`egre XX. Soit TT un KK-tore. Dans cet article, on cherche \`a \'etudier l'espace des points ad\'eliques T(S,AK)T(S,\mathbb{A}_K) de TT hors d'un ensemble fini SS de points ferm\'es de XX. On commence par montrer que le groupe T(K)T(K) des points rationnels de TT est toujours ferm\'e discret dans T(S,AK)T(S,\mathbb{A}_K). On d\'ecrit ensuite le quotient T(,AK)/T(K)T(\emptyset,\mathbb{A}_K)/T(K) dans chacun des trois cas suivants: kk corps alg\'ebriquement clos, k=C((t))k=\mathbb{C}((t)) et kk corps pp-adique.

Keywords

Cite

@article{arxiv.1801.01463,
  title  = {L'espace ad\'elique d'un tore sur un corps de fonctions},
  author = {David Harari and Diego Izquierdo},
  journal= {arXiv preprint arXiv:1801.01463},
  year   = {2018}
}

Comments

30 pages, in French. Theorem 4.5 has been improved. Section 4.2 has been added