Distortion for multifactor bimodules and representations of multifusion categories

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Main Authors: Bischoff, Marcel, Charlesworth, Ian, Evington, Samuel, Giorgetti, Luca, Penneys, David
Format: Preprint
Published: 2020
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_version_ 1866916779142414336
author Bischoff, Marcel
Charlesworth, Ian
Evington, Samuel
Giorgetti, Luca
Penneys, David
author_facet Bischoff, Marcel
Charlesworth, Ian
Evington, Samuel
Giorgetti, Luca
Penneys, David
contents We call a von Neumann algebra with finite dimensional center a multifactor. We introduce an invariant of bimodules over $\rm II_1$ multifactors that we call modular distortion, and use it to formulate two classification results. We first classify finite depth finite index connected hyperfinite $\rm II_1$ multifactor inclusions $A\subset B$ in terms of the standard invariant (a unitary planar algebra), together with the restriction to $A$ of the unique Markov trace on $B$. 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 $\rm II_1$ 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 $\rm II_1$ multifactor inclusions.
format Preprint
id arxiv_https___arxiv_org_abs_2010_01067
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle Distortion for multifactor bimodules and representations of multifusion categories
Bischoff, Marcel
Charlesworth, Ian
Evington, Samuel
Giorgetti, Luca
Penneys, David
Operator Algebras
Category Theory
Quantum Algebra
46L37, 18M20 Primary, 18M30, 18N10 Secondary
We call a von Neumann algebra with finite dimensional center a multifactor. We introduce an invariant of bimodules over $\rm II_1$ multifactors that we call modular distortion, and use it to formulate two classification results. We first classify finite depth finite index connected hyperfinite $\rm II_1$ multifactor inclusions $A\subset B$ in terms of the standard invariant (a unitary planar algebra), together with the restriction to $A$ of the unique Markov trace on $B$. 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 $\rm II_1$ 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 $\rm II_1$ multifactor inclusions.
title Distortion for multifactor bimodules and representations of multifusion categories
topic Operator Algebras
Category Theory
Quantum Algebra
46L37, 18M20 Primary, 18M30, 18N10 Secondary
url https://arxiv.org/abs/2010.01067