Seminar

The main topic of the talk will be the study of rigid geometric structures admitting a large group of  automorphisms.  Here, "large" will generally  mean noncompact.  In the first part of the talk, I will review paradigmatic examples of such structures, give a few classification results, and expose briefly Gromov's theorem describing the orbits of local automorphisms.  Then, I will explain how to use those tools to fully understand closed Lorentz 3-manifolds admitting a noncompact isometry group.