Tel-Aviv University
School of Mathematical Sciences

Department Colloquium

Monday, October 28, 2013

Schreiber 006, 12:15

Alexander Gamburd

CUNY Graduate Center

Expander Graphs, Thin Groups, and Superstrong Approximation

After introducing expander graphs and briefly discussing Lubotzky-Weiss
Independence Problem  for groups and expanders I will talk about  recent
developments pertaining to establishing the expansion property for congruence
quotients of thin groups --discrete subgroups of semi-simple groups which are
Zariski dense but of infinite index. This expansion property can be viewed as a
far-reaching generalization of the strong approximation theorem and has many

Coffee will be served at 12:00 before the lecture
at Schreiber building 006