31 Mar 2004; Mat-Nat Faculty (UITO), room U1. Wednesday 10:15-12:00 (NB: the time and place are changed!)

Vladimir Matveev (Freiburg University, Germany) "Proof of the Lichnerowicz-Obata conjecture".

The following statement will be discussed: Suppose a Lie group acts on a closed Riemannian manifold by diffeomorphisms that take (uparameterized) geodesics to geodesics. Then it acts by isometries or the metric has constant sectional curvature. 

This is the long-standing Lichnerowicz-Obata conjecture. The proof, first obtained by the author, is long, but its sketch and the main ideas will be presented in the talk.