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UID:20250908T031651EDT-9705gOzIuU@132.216.98.100
DTSTAMP:20250908T071651Z
DESCRIPTION:Title: Hyperfiniteness of the boundary action of virtually spec
 ial groups\n\nAbstract: A Borel equivalence relation on a Polish space is 
 called hyperfinite if it can be approximated by equivalence relations with
  finite classes. This notion has long been studied in descriptive set theo
 ry to measure complexity of Borel equivalence relations. Recently\, a lot 
 of research has been done on hyperfiniteness of the orbit equivalence rela
 tion on the Gromov boundary induced by various group actions on hyperbolic
  spaces. In this talk\, I will explain my attempt to explore this connecti
 on of Borel complexity and geometric group theory for another intensively 
 studied geometric object\, which is CAT(0) cube complexes. More precisely\
 , we prove that for any countable group acting virtually specially on a CA
 T(0) cube complex\, the orbit equivalence relation induced by its action o
 n the Roller boundary is hyperfinite.\n
DTSTART:20250903T070000Z
DTEND:20250903T080000Z
LOCATION:Room 1104\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue
  Sherbrooke Ouest
SUMMARY:Koichi Oyakawa (ÂÌñÉç)
URL:/channels/channels/event/koichi-oyakawa-mcgill-366
 953
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