Homology and cohomology of crossed products by inverse monoid actions and Steinberg algebras

Abstract

Given a unital action $\theta$ of an inverse monoid $S$ on an algebra $A$ over a filed $K$ we produce (co)homology spectral sequences which converge to the Hochschild (co)homology of the crossed product $A{⋊}_{\theta }S$ with values in a bimodule over $A{⋊}_{\theta }S$. The spectral sequences involve a new kind of (co)homology of the inverse monoid $S,$ which is based on $KS$-modules. The spectral sequences take especially nice form, when $(A{⋊}_{\theta }S{)}^e$ is flat as a left (homology case) or right (cohomology case) $A^e$-module, involving also the Hochschild (co)homology of $A.$ Same nice spectral sequences are also obtained if $K$ is a commutative ring, over which $A$ is projective, and $S$ is $E$-unitary. We apply our results to the Steinberg algebra $A_K(\mathcal{G})$ over a field $K$ of an ample groupoid $\mathcal{G},$ whose unit space ${\mathcal{G}}^{(0)}$ is compact. In the homology case our spectral sequence collapses on the $p$-axis, resulting in an isomorphism between the Hochschild homology of $A_K(\mathcal{G})$ with values in an $A_K(\mathcal{G})$-bimodule $M$ and the homology of the inverse semigroup of the compact open bisections of $\mathcal{G}$ with values in the invariant submodule of $M.$