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Property (T) and approximate conjugacy of actions

Presented by: 
Andreas Aaserud Cardiff University
Date: 
Thursday 20th April 2017 - 10:00 to 11:00
Venue: 
INI Seminar Room 2
Abstract: 
I will define a notion of approximate conjugacy for probability measure preserving actions and compare it to the a priori stronger classical notion of conjugacy for such actions. In particular, I will spend most of the talk explaining the proof of a theorem stating that two ergodic actions of a fixed group with Kazhdan's property (T) are approximately conjugate if and only if they are actually conjugate. Towards this end, I will discuss some constructions from the theory of von Neumann algebras, including the basic construction of Vaughan Jones and a version of the Feldman-Moore construction. I will also provide some evidence that this theorem may yield a characterization of groups with Kazhdan's property (T).   (Joint work with Sorin Popa)



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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons