IIAS Seminar: Tatiana Nagnibeda - Infinite Ramanujan graphs and completely dissipative actions

Speaker : Tatiana Nagnibeda (University of Geneva) Abstract: The definition of a Ramanujan graph extends naturally to infinite graphs: an infinite graph is Ramanujan if its spectral radius is not larger than (and hence equal to) the spectral radius of its universal covering tree. As with infinite families of finite graphs, it is interesting and non-trivial to understand, how much Ramanujan graphs resemble trees. I will discuss some results in this direction obtained in a joint work with Vadim Kaimanovich, by investigating ergodic properties of boundary actions of free groups.

Date: 

Tue, 05/09/2017 - 16:00 to 17:00

Location: 

Math room 209