Constructing equivariant vector bundles via the BGG correspondence

Abstract

We describe a strategy for the construction of finitely generated $G$-equivariant $\mathbb{Z}$-graded modules $M$ over the exterior algebra for a finite group $G$. By an equivariant version of the BGG correspondence, $M$ defines an object $\mathcal{F}$ in the bounded derived category of $G$-equivariant coherent sheaves on projective space. We develop a necessary condition for $\mathcal{F}$ being isomorphic to a vector bundle that can be simply read off from the Hilbert series of $M$. Combining this necessary condition with the computation of finite excerpts of the cohomology table of $\mathcal{F}$ makes it possible to enlist a class of equivariant vector bundles on $\mathbb{P}^4$ that we call strongly determined in the case where $G$ is the alternating group on $5$ points.