Semiinfinite cohomology of quantum groups

Abstract

In this paper we develop a new homology theory of associative algebras called semiinfinite cohomology in a derived category setting. We show that in the case of small quantum groups the zeroth semiinfinite cohomology of the trivial module is closely related to the conformal blocks' spaces. We provide a description of the semiinfinite cohomology spaces of the trivial module over a small quantum group in terms of distributions on the nilpotent cone of the corresponding semisimple Lie algebra.