EVENT DETAILS AND ABSTRACT

Title: The measurable Kesten theorem
Speaker: Miklos Abert
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Abstract:

Let Gamma be a finitely generated group and N be a normal subgroup. Kesten's theorem (essentially his thesis) says that a random walk of Gamma sees N with exponentially larger probability than it sees the identity, if and only if N is a non-amenable group. It is easy to see that this theorem is false when one omits the normality condition. In the talk I will extend Kesten's result in the measurable setting and show what this implies on the geometry of Ramanujan graphs. This is joint work with Yair Glasner and Balint Virag.