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arXiv · 0707.1458

Explicit computations of all finite index bimodules for a family of II_1 factors

Stefaan Vaes
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Abstract

We study II_1 factors M and N associated with good generalized Bernoulli actions of groups having an infinite almost normal subgroup with the relative property (T). We prove the following rigidity result: every finite index M-N-bimodule (in particular, every isomorphism between M and N) is described by a commensurability of the groups involved and a commensurability of their actions. The fusion algebra of finite index M-M-bimodules is identified with an extended Hecke fusion algebra, providing the first explicit computations of the fusion algebra of a II_1 factor. We obtain in particular explicit examples of II_1 factors with trivial fusion algebra, i.e. only having trivial finite index subfactors.

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Stefaan Vaes. 2008-02-11. Explicit computations of all finite index bimodules for a family of II_1 factors. https://arxiv.org/abs/0707.1458

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