ANNULÉ/CANCELLED - Tarski numbers of non-amenable groups and group actions (Corentin Bodart, Université de Genève)

27.10.2020 10:30

This talk is splitted in two parts. First we'll classify some paradoxical decompositions of the (non-abelian) free group of rank 2. As a corollary we recover a classical result of Jónsson on group actions with Tarski number 4. Next we present recent estimations on isoperimetric constants of groups in term of their cost, using random forests. We briefly explain how those estimations were used by Ershov, Golan and Sapir to construct the first examples of groups with Tarski numbers 5 and 6.

Lieu

Room 623
Séminaire Groupes et Géométrie

entrée libre