Cosimplicial monoids and deformation theory of tensor categories

Abstract

We introduce the notion of $n$-commutativity ($0\le n\le \infty$) for cosimplicial monoids in a symmetric monoidal category $\mathbf{V}$, where $n=0$ corresponds to just cosimplicial monoids in $\mathbf{V}$, while $n=\infty$ corresponds to commutative cosimplicial monoids. When $\mathbf{V}$ has a monoidal model structure, we endow (under some mild technical conditions) the total object of an $n$-cosimplicial monoid with a natural and very explicit $E_{n+1}$-algebra structure.

Our main applications are to the deformation theory of tensor categories and tensor functors. We show that the deformation complex of a tensor functor is a total complex of a $1$-commutative cosimplicial monoid and, hence, has an $E_2$-algebra structure similar to the $E_2$-structure on Hochschild complex of an associative algebra provided by Deligne's conjecture. We further demonstrate that the deformation complex of a tensor category is the total complex of a $2$-commutative cosimplicial monoid and, therefore, is naturally an $E_3$-algebra. We make these structures very explicit through a language of Delannoy paths and their noncommutative liftings. We investigate how these structures manifest themselves in concrete examples.