Hodge theory for group cohomology and local rigidity

David Fisher (University of Indiana)

Abstract: I will discuss a far ranging generalization of (one aspect of) property (T): the relation between vanishing of cohomology and vanishing of reduced cohomology. The generalization applies to cohomology in all degrees and to a wide variety of classes of representations. The main ingredient is a form of Hodge theory for group cohomology. I will also discuss applications to local rigidity and if time permits to cohomology of lattices in Lie groups.