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DESCRIPTION:✒️ TITLE / TITRE\n\nOrbit equivalence relations and the compact
  action realization problem\n\n \n\n📄 ABSTRACT / RÉSUMÉ\n\nThe study of or
 bit equivalence relations induced by Borel actions of countable groups on 
 Polish (separable completely metrizable) spaces\, and their orbit spaces\,
  has been a very active area of research for several decades in various fi
 elds of mathematics\, including ergodic theory\, operator algebras\, geome
 tric group theory\, combinatorics\, probability and descriptive set theory
 . Many results in this area have been obtained using ergodic (measure theo
 retic) methods. After giving a basic introduction to this theory\, I will 
 focus on a new direction of topological nature that deals with the problem
  of realizing orbit equivalence relations by continuous actions on compact
  metrizable spaces and in particular subshifts. This also leads to conside
 ring a natural universal space for such actions and equivalence relations 
 via subshifts and originates the study in this space of various important 
 classes\, especially the so-called hyperfinite ones\, which are those indu
 ced by actions of the group of integers. This is joint work with Josh Fris
 ch\, Forte Shinko and Zoltan Vidnyánszky.\n\n📍 PLACE / LIEU \n	Hybride - CR
 M\, Salle / Room 5340\, Pavillon André Aisenstadt\n	 \n
DTSTART:20260407T144500Z
DTEND:20260407T144500Z
SUMMARY:Alexander Kechris (Caltech)
URL:/mathstat/channels/event/alexander-kechris-caltech
 -372285
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