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Logic Seminar

Wednesday, February 16, 2022
12:00pm to 1:00pm
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Online Event
Orbit equivalences of multidimensional Borel flows
Konstantin Slutsky, Department of Mathematics, Iowa State University,

An orbit equivalence between Borel actions of Polish groups is a Borel bijection between phase spaces that preserves orbit partitions. We are interested in free Rm-actions which are known as multidimensional flows. In this case, orbit equivalence is a coarse invariant collapsing all non-trivial flows into one class. Since any translation-invariant structure can be transferred from the acting group onto individual orbits, it is natural to consider strengthenings of orbit equivalence that respect these structures. Notable examples of such structures include measure, topology, and metric. We will concentrate on two instances of this paradigm and discuss Borel versions of two ergodic-theoretical results: Katok's representation theorem and Rudolph's result on smooth orbit equivalence. The latter shows that any non-trivial free Rm-flow can be transformed into any other Rm-flow via an orbit equivalence that is a smooth orientation-preserving diffeomorphism on each orbit. Katok's theorem provides a multidimensional generalization of the suspension flow construction and shows that all free Rm-flows emerge as special flows over Zm-actions.

For more information, please contact Math Dept. by phone at 626-395-4335 or by email at A. Kechris at [email protected].