Analytic R-groups of affine Hecke algebras
arXiv:0909.1227
Abstract
We define analytic -groups for affine Hecke algebras, and prove the analog of the Knapp-Stein Dimension Theorem. As a corollary we prove that the commutant algebra of a unitary principal series representation is isomorphic to the complex group algebra of the -group, twisted by a certain 2-cocycle . For classical Hecke algebras we prove that is always trivial.
Some improvements in the presentation were made, and an example has been added showing the nontriviality of the cohomology class of the 2-cocycle (as opposed to itself) for Hecke algebras of type D