Algebraic and analytic Dirac induction for graded affine Hecke algebras

TL;DR

This paper introduces an algebraic Dirac induction map for graded affine Hecke algebras, establishing an isometric isomorphism between elliptic characters and connecting algebraic and analytic methods to realize discrete series modules.

Contribution

It defines a uniform algebraic Dirac induction map for graded affine Hecke algebras and links elliptic characters to discrete series representations through analytic Dirac operators.

Findings

The map $ ext{Ind}_D$ is an isometric isomorphism between elliptic characters.

All irreducible discrete series modules are realized as kernels of Dirac operators.

The construction parallels discrete series for semisimple Lie groups.

Abstract

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 definition of $\Ind_D$ is uniform over the parameter space of the graded affine Hecke algebra. We show that the map $\Ind_D$ defines an isometric isomorphism from the space of elliptic characters of the Weyl group (relative to its reflection representation) to the space of elliptic characters of the graded affine Hecke algebra. We also study a related analytically defined 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 Hecke algebra analogue of the construction of discrete series representations for semisimple Lie groups due to Parthasarathy and Atiyah-Schmid.