A Classification of Modular Functors via Factorization Homology

Fuente: arXiv
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Autores principales: Brochier, Adrien, Woike, Lukas
Formato: Preprint
Publicado: 2022
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author Brochier, Adrien
Woike, Lukas
author_facet Brochier, Adrien
Woike, Lukas
contents Modular functors are traditionally defined as systems of projective representations of mapping class groups of surfaces that are compatible with gluing. They can formally be described as modular algebras over central extensions of the modular surface operad, with the values of the algebra lying in a suitable symmetric monoidal $(2,1)$-category $\mathcal{S}$ of linear categories. In this paper, we prove that modular functors in $\mathcal{S}$ are equivalent to self-dual balanced braided algebras $\mathcal{A}$ in $\mathcal{S}$ (a categorification of the notion of a commutative Frobenius algebra) for which a condition formulated in terms of factorization homology with coefficients in $\mathcal{A}$ is satisfied; we call such $\mathcal{A}$ connected. The equivalence in one direction is afforded by genus zero restriction. Our construction of the inverse equivalence is entirely topological and can be thought of as a far reaching generalization of the construction of modular functors from skein theory. In order to verify the connectedness condition in practice, we prove that it can be reduced to a single condition in genus one. Moreover, we show that cofactorizability of $\mathcal{A}$, a condition known to be satisfied for modular categories, is sufficient. Therefore, we recover in particular Lyubashenko's construction of a modular functor from a (not necessarily semisimple) modular category and show that it is determined by its genus zero part. Additionally, we exhibit modular functors that do not come from modular categories and outline applications to the theory of vertex operator algebras.
format Preprint
id arxiv_https___arxiv_org_abs_2212_11259
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle A Classification of Modular Functors via Factorization Homology
Brochier, Adrien
Woike, Lukas
Quantum Algebra
Algebraic Topology
Representation Theory
Modular functors are traditionally defined as systems of projective representations of mapping class groups of surfaces that are compatible with gluing. They can formally be described as modular algebras over central extensions of the modular surface operad, with the values of the algebra lying in a suitable symmetric monoidal $(2,1)$-category $\mathcal{S}$ of linear categories. In this paper, we prove that modular functors in $\mathcal{S}$ are equivalent to self-dual balanced braided algebras $\mathcal{A}$ in $\mathcal{S}$ (a categorification of the notion of a commutative Frobenius algebra) for which a condition formulated in terms of factorization homology with coefficients in $\mathcal{A}$ is satisfied; we call such $\mathcal{A}$ connected. The equivalence in one direction is afforded by genus zero restriction. Our construction of the inverse equivalence is entirely topological and can be thought of as a far reaching generalization of the construction of modular functors from skein theory. In order to verify the connectedness condition in practice, we prove that it can be reduced to a single condition in genus one. Moreover, we show that cofactorizability of $\mathcal{A}$, a condition known to be satisfied for modular categories, is sufficient. Therefore, we recover in particular Lyubashenko's construction of a modular functor from a (not necessarily semisimple) modular category and show that it is determined by its genus zero part. Additionally, we exhibit modular functors that do not come from modular categories and outline applications to the theory of vertex operator algebras.
title A Classification of Modular Functors via Factorization Homology
topic Quantum Algebra
Algebraic Topology
Representation Theory
url https://arxiv.org/abs/2212.11259