**Date & Time:** Wednesday, November 19, 2014, 16:00-17:00.

**Venue:** Ramanujan Hall

**Speaker:** Alex Gorodnik, University of Bristol

**Title:** Diophantine approximation by orbits

**Abstract:** The classical theory of Diophantine approximation quantifies the
density of rational number in the real line. In a joint work with A.
Ghosh and A. Nevo we consider an analogous problem of approximating by
dense orbits for group actions. We explain a general
approach which allows to establish quantitative density and gives the
best possible exponents of approximation in a number of cases.