ALGEBRAIC AND ANALYTIC DIRAC INDUCTION FOR GRADED AFFINE HECKE ALGEBRAS

摘要

We define the algebraic Dirac induction map Ind_D for graded affine Hecke algebras. The map Ind_D is a Hecke algebra analog of the explicit realization of the Baum-Connes assembly map in the K-theory of the reduced C*-algebra of a real reductive group using Dirac operators. The de nition of IndD is uniform over the parameter space of the graded affine Hecke algebra. We show that the map IndD de nes an isometric isomorphism from the space of elliptic characters of the Weyl group (relative to its re ection representation) to the space of elliptic characters of the graded affine Hecke algebra. We also study a related analytically de ned global elliptic Dirac operator between unitary representations of the graded affine Hecke algebra which are realized in the spaces of sections of vector bundles associated to certain representations of the pin cover of the Weyl group. In this way we realize all irreducible discrete series modules of the Hecke algebra in the kernels (and indices) of such analytic Dirac operators. This can be viewed as a graded affine Hecke algebra analog of the construction of the discrete series representations of semisimple Lie groups due to Parthasarathy and to Atiyah and Schmid.