II_1 factors with non-isomorphic ultrapowers

Remi Boutonnet (Institut de Mathématiques de Bordeaux)

Tuesday 3rd May, 2016 16:00-17:00 Maths 522


In this talk I will present recent joint work with Ionut Chifan and Adrian Ioana showing that there exist infinitely many II1 factors with non-isomorphic ultrapowers. More precisely, we construct a concrete family of factors whose ultrapowers can be distinguished by computing a new invariant for von Neumann algebras. This invariant relies on the notion of central sequence.

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