Piotr Nowak, Texas A&M University
Amenable actions and quasi-invariant measures

We will discuss amenable actions and present conditions which imply that an action of a non-amenable group or a non-a-T-menable group is not amenable. These conditions are expressed in terms of the existence of a quasi-invariant measure which is sufficiently close to being invariant. As a corollary we will show non-amenability of certain actions of the free group on the circle. This is joint work with Ron Douglas.