Séminaires : Séminaire d'Algèbres d'Opérateurs

Equipe(s) : ao,
Responsables :Pierre Fima, François Le Maître, Romain Tessera
Email des responsables :
Salle : 1013
Adresse :Sophie Germain

Orateur(s) Eduardo Scarparo - Norwegian University of Science and Technology,
Titre Boundary maps, germs and quasi-regular representations
Horaire14:00 à 15:00
Diffusion https://bigbluebutton3.imj-prg.fr/b/fra-j6k-9fw
RésumeIn recent years, there have been great advances in understanding when the reduced C*-algebra of a discrete group is simple and when it has the unique trace property. A central role in these discoveries has been played by Furstenberg's notion of boundary action (specially the so-called Furstenberg boundary). For quasi-regular representations in general, the situation is much different, with Haagerup and Olesen showing that there is such a representations \pi of Thompson's group V such that C*_\pi(V) is the Cuntz algebra O_2 (hence simple and without traces). In this talk, we will review the notions above, and present applications of boundary actions to the study of invariant random subgroups, traces and C*-simplicity of quasi-regular and Koopman representations. We will be specially interested in representations of Thompson's groups. This is joint work with Mehrdad Kalantar.
AdresseSophie Germain