An analog of the Deligne-Lusztig duality for $(\mathfrak{g},K)$-modules

TL;DR

This paper extends Drinfeld's pseudo-identity functor to DG categories, demonstrating its role as an inverse to the Serre functor and proposing it as an analog of the Deligne-Lusztig duality for (g,K)-modules.

Contribution

It introduces a generalized pseudo-identity functor for DG categories and establishes its equivalence to the inverse of the Serre functor, applying it to (g,K)-modules as an analog of Deligne-Lusztig duality.

Findings

Pseudo-identity functor is inverse of the Serre functor under finiteness conditions.

Pseudo-identity functor for (g,K)-modules is isomorphic to composition of dualities.

Supports analogy with p-adic groups in representation theory.

Abstract

Drinfeld suggested the definition of a certain endo-functor, called the pseudo-identity 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 (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 (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 [BBK].