Let G be a group. A subgroup H of G is a Cartan subgroup ofG if H is a maximal nilpotent subgroup of G, and for every normal finiteindex subgroup X of H, X has finite index in its normalizer in G.We consider Cartan subgroups of definably connect groups definable inan o-minimal structure. In we proved that, in this context,Cartan subgroups of G exist, they are definable and they fall infinitely many conjugacy classes.In this talk I will prove that the union of the Cartan subgroups isdense in the group, […]

Using ultraproducts, I will describe the spectrum of the profinite completion of the integers and of the finite adeles over the rationals.The final aim is to describe the structure sheaf of these structures.Joint work with Margarita Otero and Angus Macintyre.

Nous présenterons une preuve de la Propriété (T) de Kazhdan pour les groupes d'automorphismes de structures métriques aleph_0-catégoriques. Ceci généralise des résultats précédents de Bekka (pour le groupe unitaire) et de Evans et Tsankov (pour les groupes pro-oligomorphes), sans besoin de faire appel à des résultats de classification de représentations unitaires. En effet, l'argument est purement modèle-théorique et basé sur des principes de la stabilité locale.

There is a well-known analogy between the arithmetic of rational numbers and the theory of meromorphic functions over a normed field. It is a classical result of Julia Robinson that the first order theory of the field of rational numbers is undecidable, and one would expect such a result in the meromorphic setting. In this talk I'll give an outline of the proof of undecidability for rigid meromorphic functions in positive characteristic