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DTSTART:19700329T010000
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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Approximate equivalence of measure-preserving acti
ons - Andreas Aaserud (Cardiff University)
DTSTART;TZID=Europe/London:20170309T140000
DTEND;TZID=Europe/London:20170309T150000
UID:TALK71433AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/71433
DESCRIPTION:I will talk about measure-preserving actions of co
untable discrete groups on probability spaces. Cla
ssically\, one mainly considers two notions of equ
ivalence of such actions\, namely conjugacy (or is
omorphism) and orbit equivalence\, both of which h
ave nice descriptions in the language of von Neuma
nn algebras. \;I will briefly discuss this cla
ssical framework before going into some new notion
s of equivalence of actions. These are approximate
versions of conjugacy and orbit equivalence that
were recently introduced and investigated by Sorin
Popa and myself\, and which can \;most easily
be defined in terms of ultrapowers of von Neumann
algebras. I will discuss superrigidity within thi
s new framework\, and \;will also compare appr
oximate conjugacy to (classical) conjugacy for act
ions of various classes of groups. This talk is ba
sed on joint work with Sorin Popa.

LOCATION:Seminar Room 2\, Newton Institute
CONTACT:INI IT
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