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DTSTART:20240310T070000
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DTSTART:20241103T060000
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DTSTART;TZID=America/Toronto:20250220T160000
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URL:https://uwaterloo.ca/pure-mathematics/events/analysis-seminar-190
SUMMARY:Analysis Seminar
CLASS:PUBLIC
DESCRIPTION:BECKY ARMSTRONG\, VICTORIA UNIVERSITY OF WELLINGTON\n\nAnalysis
  Seminar: Twisted groupoids that are not induced by continuous\n2-cocycles
 \n\nTwisted groupoids are generalisations of group extensions that play an
 \nimportant role in C*-algebraic theory: every classifiable C*-algebra\nha
 s an underlying twisted groupoid model. It is well known that group\nexten
 sions are in one-to-one correspondence with group 2-cocycles.\nAnalogously
 \, every groupoid 2-cocycle gives rise to a twisted\ngroupoid. However\, a
 n example due to Kumjian shows that the converse\nis not true. Kumjian’s
  counterexample is a twisted groupoid\nconsisting entirely of isotropy\, b
 ut in this talk I will present a new\nexample of a twisted groupoid that i
 s not all isotropy\, such that the\ntwisted isotropy subgroupoid is not in
 duced by a 2-cocycle. (This is\njoint work with Abraham C.S. Ng\, Aidan Si
 ms\, and Yumiao Zhou.) \n\nMC 5417
DTSTAMP:20260504T185934Z
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