Mathematical logic seminar - October 6, 2015

Time: 12:30 - 13:30

Room: Wean Hall 7201

Speaker:     Clinton Conley    
Department of Mathematical Sciences

Title: Borel marker sets and hyperfiniteness II

Abstract: We show using measure-theoretic techniques that every nonamenable group has a Borel action with non-hyperfinite equivalence relation. We then discuss the limitations of such measure-theoretic arguments in further narrowing the class of groups with all actions hyperfinite, and, time permitting, present results of Weiss and Jackson-Kechris-Louveau giving noncyclic examples of such groups.