Logic Date:  Thursday, February 28, 2013 Location:  2866 East Hall (4:00 PM to 5:30 PM) Title:  Countable locally nilpotent group actions and hyperfinite equivalence relations Abstract:   An equivalence relation E is hyperfinite if E is the increasing union of a sequence of Borel equivalence relations with finite classes. In 1982 Weiss proved that any orbit equivalence relation arising from a Borel action of Z is hyperfinite, and asked whether this property is shared by larger classes of countable groups. We survey this question and discuss recent positive answers to it by Gao and Jackson for abelian groups, and by Seward and the speaker for free actions of locally nilpotent groups. Speaker:  Scott Schneider Institution:  University of Michigan Event Organizer:   Andreas Blass      Edit this event (login required). Add new event (login required). For access requests and instructions, contact math-webmaster@umich.edu Back to previous page Back to UM Math seminars/events page.