Technion Mathematics Colloquium Speaker: Alexander Gamburd (CUNY Graduate Center) Title: Expander Graphs, Thin Groups and Super-strong Approximation Time: Monday, January 23, 3:30 pm Place: Amado 232, Technion Colloquium Homepage: <http://www.technion.ac.il/~yehuday/colloquium/colloq.html> Abstract: 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 semisimple 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 applications, in particular to affine linear sieve. --------------------------------------------------------- Technion Math. Net (TECHMATH) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Amir Yehudayoff <amir.yehudayoff@gmail.com>