Highest weight modules at the critical level and noncommutative Springer resolution

Abstract

In the article by Bezrukavnikov and Mirkovic a certain non-commutative algebra A was defined starting from a semi-simple algebraic group, so that the derived category of A-modules is equivalent to the derived category of coherent sheaves on the Springer (or Grothendieck-Springer) resolution. Let gˇ be the Langlands dual Lie algebra and let [˄ over g] be the corresponding affine Lie algebra, i.e. [˄ over g] is a central extension of gˇ ⊗ C((t)). Using results of Frenkel and Gaitsgory we show that the category of [˄ over g] modules at the critical level which are Iwahori integrable and have a fixed central character, is equivalent to the category of modules over a central reduction of A. This implies that numerics of Iwahori integrable modules at the critical level is governed by the canonical basis in the K-group of a Springer fiber, which was conjecturally described by Lusztig and constructed by Bezrukavnikov and Mirkovic.