Séminaires : Séminaire de Logique Lyon-Paris

Equipe(s) : lm,
Responsables :O. Finkel, A. Khélif, S. Rideau, T. Tsankov, A. Vignati
Email des responsables :
Salle : Zoom ID: 824 8220 9628; s'inscrire à la liste ou contacter silvain.rideau@imj-prg.fr pour le mot de passe.
Adresse :
Description

ArchivesRetour ligne automatique
Abonnement à la liste de diffusion


Orateur(s) Philipp Schlicht - Bristol University,
Titre Oligomorphic groups are essentially countable
Date09/12/2019
Horaire15:15 à 16:15
Diffusion
Résume
Model theoretic properties of a countable structure are closely connected with properties of its automorphism group. For instance, the automorphism groups of ω-categorical structures on N are precisely the oligomorphic closed subgroups of Sym(N) (a permutation group is oligomorphic if for each k there are only finitely many k-orbits). We study the complexity of topological isomorphism of oligomorphic closed subgroups of Sym(N) in the setting of Borel reducibility. Previous work of Kechris, Nies and Tent, and independently Rosendal and Zielinski, showed that this equivalence relation is below graph isomorphism. We show that it is below a Borel equivalence relation with countable equivalence classes. This is joint work with Andre Nies and Katrin Tent. 
Salle2015
AdresseSophie Germain
© IMJ-PRG