Matthieu Joseph: "Rigidity and flexibility phenomenons in isometric orbit equivalence"

mardi 9 févr. 2021, 10:15 → 11:15 Europe/Paris

Abstract: In an ongoing work, we introduce the notion of isometric orbit equivalence for probability measure preserving actions of marked groups. This notion asks the Schreier graphings defined by the actions of the marked groups to be isomorphic. In the first part of the talk, we will prove that pmp actions of a marked group whose Cayley graph has a discrete automorphisms group are rigid up to isometric orbit equivalence. In a second time, we will explain how to construct pmp actions of the free group that are isometric orbit equivalent but not (virtually) conjugate.