English

Distortion for multifactor bimodules and representations of multifusion categories

Operator Algebras 2025-06-06 v1 Category Theory Quantum Algebra

Abstract

We call a von Neumann algebra with finite dimensional center a multifactor. We introduce an invariant of bimodules over II1\rm II_1 multifactors that we call modular distortion, and use it to formulate two classification results. We first classify finite depth finite index connected hyperfinite II1\rm II_1 multifactor inclusions ABA\subset B in terms of the standard invariant (a unitary planar algebra), together with the restriction to AA of the unique Markov trace on BB. 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 II1\rm II_1 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 II1\rm II_1 multifactor inclusions.

Keywords

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

R2 v1 2026-06-23T18:58:38.066Z