  Let G be an algebraic group over an algebraically closed field of positive
characteristic such that its neutral connected component is a unipotent group.
We consider a certain class of closed idempotents in the braided monoidal
category (under convolution of complexes) D_G(G) known as Heisenberg
idempotents. For such an idempotent e, we will prove certain results about the
Hecke subcategory eD_G(G) conjectured by V. Drinfeld. In particular, we will
see that it is the bounded derived category of a modular category.
