School Seminars and Colloquia

Very unfree countable Borel equivalence relations

School Seminar

by Professor Greg Hjorth

Institution: Department of Mathematics & Statistics, The University of Melbourne
Date: Wed 4th April 2007
Time: 4:30 PM
Location: Room 107, Richard Berry Building

Abstract: Following work of Scot Adams, we know that not every
countable Borel equivalence relation is induced by the free Borel action of a countable group. By Alex Furman, such counterexamples
exist even if we allow ourselves to discard a null set. I will talk about some recent work of Sorin Popa and Simon Thomas and concerning
Borel reduction to free actions and some extensions of the Adams-Furman results.

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