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Bass-serre rigidity results in von neumann algebras
Journal article   Peer reviewed

Bass-serre rigidity results in von neumann algebras

Ionut Chifan and Cyril Houdayer
Duke Mathematical Journal, Vol.153(1), pp.23-54
2010
DOI: 10.1215/00127094-2010-020
url
https://arxiv.org/pdf/0805.1566View
Open Access

Abstract

We obtain new Bass-Serre-type rigidity results for II1 equivalence relations and their von Neumann algebras, coming from free ergodic actions of free products of groups on the standard probability space. As an application, we show that any nonamenable factor arising as an amalgamated free product of von Neumann algebras M1 *B M2 over an abelian von Neumann algebra B is prime, that is, cannot be written as a tensor product of diffuse factors. This gives, both in the type II1 and in the type III cases, new examples of prime factors. © 2010.

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