Seminario Teoría de grupos 20/01

11:30 Aula Gris 2 ICMAT

Speaker: Sam Fisher (University of Oxford)

Title: L^2-Betti numbers and algebraic fibring

Abstract: We introduce the theory of L^2-invariants and explain their relation to algebraic fibring of groups. In particular, if a group is virtually algebraically fibred, then its L^2-Betti numbers vanish. We also present a converse of this result for the class of virtually RFRS groups, which include RAAGs, RACGs, and special groups, as well as subgroups, products, and free products of all these groups. A positive characteristic version of this result is also presented.