The Heisenberg algebra of a vector space and Hochschild homology

Abstract

For any noncommutative smooth and proper variety we construct three actions of the Heisenberg algebra on the total Hochschild homology of its symmetric quotient stacks. One is defined algebraically using the orbifold decomposition of Hochschild homology. One decategorifies the 2-categorical Heisenberg action of Gyenge-Koppensteiner-Logvinenko. One is defined representation theoretically via explicit operators intrinsic to the symmetric quotient stacks. We then show all three to coincide, and thus give alternative descriptions of one natural action. For ordinary commutative varities, we give a fourth, geometrical description by correspondences similar to those used by Grojnowski and Nakajima for the Hilbert schemes of points on surfaces.

54 pages; v2; the results significantly strengthened and expanded: the decategorified action from v1 is computed explicitly, leading to alternative constructions of this action by algebraic, representation-theoretic, and geometric means. 50 percent of the paper rewritten. Introduction and abstract completely rewritten. The material on PQ-generators removed to a separate paper