Multiplicative structure on the Hochschild cohomology of crossed product algebras

Abstract

Consider a smooth affine algebraic variety $X$ over an algebraically closed field, and let a finite group $G$ act on it. We assume that the characteristic of the field is greater than the dimension of $X$ and the order of $G$. An explicit formula for multiplication on the Hochschild cohomology of a crossed product of $k[G]$ and $k[X]$ is given in terms of multivector fields on $X$ and $g$-invariant subvarieties of $X$ for $g\in G$.

9 pages; the Gerstenhaber bracket part withdrawn on 12/08/05 due to a gap in one of the proofs. Some references added