Algebra and Geometry Seminar

This is joint work with Dennis Gaitsgory.

Drinfeld suggested the definition of a certain endo-functor, called the pseudo-identity functor (or the Drinfeld-Gaitsgory functor), on the category of D-modules on an algebraic stack. We extend this definition to an arbitrary DG category, and show that if certain finiteness conditions are satisfied, this functor is the inverse of the Serre functor. We apply this to the category of $(\mathfrak{g},K)$-modules, and we stipulate that the pseudo-identity functor is the analog of the Deligne-Lusztig functor. In order to support this, we show that the pseudo-identity functor for $(\mathfrak{g},K)$-modules is isomorphic to the composition of cohomological and contragredient dualities, which is parallel to the corresponding assertion for p-adic groups in the work of Bernstein, Bezrukavnikov and Kazhdan.

In this talk I will try to talk about the setting and ingredients of these results.