Distortion for multifactor bimodules and representations of multifusion categories
Abstract
We call a von Neumann algebra with finite dimensional center a multifactor. We introduce an invariant of bimodules over multifactors that we call modular distortion, and use it to formulate two classification results. We first classify finite depth finite index connected hyperfinite multifactor inclusions in terms of the standard invariant (a unitary planar algebra), together with the restriction to of the unique Markov trace on . The latter determines the modular distortion of the associated bimodule. Three crucial ingredients are Popa's uniqueness theorem for such inclusions which are also homogeneous, for which the standard invariant is a complete invariant, a generalized version of the Ocneanu Compactness Theorem, and the notion of Morita equivalence for inclusions. Second, we classify fully faithful representations of unitary multifusion categories into bimodules over hyperfinite multifactors in terms of the modular distortion. Every possible distortion arises from a representation, and we characterize the proper subset of distortions that arise from connected multifactor inclusions.
Cite
@article{arxiv.2010.01067,
title = {Distortion for multifactor bimodules and representations of multifusion categories},
author = {Marcel Bischoff and Ian Charlesworth and Samuel Evington and Luca Giorgetti and David Penneys},
journal= {arXiv preprint arXiv:2010.01067},
year = {2025}
}
Comments
71 pages, many figures