Questions de corps de définition pour les variétés abéliennes en caractéristique positive

Franck Benoist (1) , Françoise Delon (2)

1 Albert-Ludwigs-Universität Freiburg
2 ELM - Équipe de Logique Mathématique

Dichotomies in various conjectures from algebraic geometry are in fact occurrences of the dichotomy among Zariski structures. This is what Hrushovski showed and which enabled him to solve, positively, the geometric Mordell Lang conjecture in positive characteristic. Are we able now to avoid this use of Zariski structures? Pillay and Ziegler have given a direct proof that works for abelian varieties they called ``very thin'', which include the ordinary abelian varieties. But it does not apply in all generality: We describe here an abelian variety which is not very thin. More generally, we consider from a model-theoretical point of view several questions about the fields of definition of semi-abelian varieties.

Mots clés: abelian varieties; Mordell-Lang; thinness; Hasse derivation; Weil restriction; fields of definition; p-torsion; Newton polygon; separability

Domaines: Logique [math.LO]

Franck Benoist, Françoise Delon. Questions de corps de définition pour les variétés abéliennes en caractéristique positive. 2008. ⟨hal-00137362v2⟩