Logic Seminar
Inessa Epstein
UCLA
The Borel complexity of orbit equivalence of ergodic actions of non-amenable groups
Abstract: We consider a countable group G acting in a Borel way by measure preserving automorphisms on a standard probability space X. The orbits of this action give rise to an equivalence relation on X. We say two measure preserving actions of groups G and H on spaces X and Y, respectively, are orbit equivalent if there is a measure preserving bijection between conull subsets of X and Y identifying the orbits. We discuss the complexity of the classification problem of free, measure preserving, ergodic actions of a countable group under orbit equivalence and show that it is not classifiable by countable structures.
The seminar begins with tea.
Tuesday August 26, 2008 at 4:00 PM in SEO 612