## Topology & Geometric Group Theory Seminar

## Spring 2009

### 1:30 – 2:30, Malott 207

Thursday, March 26

**Amir
Mohammadi**, Yale University

*Unipotent flows in positive characteristic and applications*

Over the past 40 years or so unipotent flow on homogeneous spaces and
its applications to number theory, especially to Diophantine
approximation, has attracted considerable attention. Margulis's proof
of the Oppenheim conjecture and Ratner's seminal work on the proof of
Raghunathan's conjecture are two very important landmarks in the
field. Although Raghunathan's conjecture in characteristic zero is
settled, the question in positive characteristic is wide open. In
this talk we will address recent progress on this question. In
particular we will report on joint work with M. Einsiedler on
classification of joinings for certain unipotent flows. This has
applications to quasi-isometry rigidity of lattices.

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