Operator Algebra seminar

Speaker: Rémi Boutonnet (University of Bordeaux)

Title: Local spectral gap for translation actions

Abstract: I will report on joint works with Adrian Ioana and Alireza Salehi Golsefidi. We study translation actions, that is, actions obtained by left multiplication on a locally compact group G by elements in a countable dense subgroup of G. Such actions preserve the Haar measure, which is infinite when the group G is not compact. In this infinite setting I will explain how to define a notion of local spectral gap which generalizes the usual (very useful) notion of spectral gap from the compact setting.