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Algebraic and analytic Dirac induction for graded affine Hecke algebras

Published online by Cambridge University Press:  13 March 2013

Dan Ciubotaru ,
Eric M. Opdam  and
Peter E. Trapa
Dan Ciubotaru
Affiliation:
Department of Mathematics, University of Utah, Salt Lake City, UT 84112, USA (ciubo@math.utah.edu; ptrapa@math.utah.edu)
Eric M. Opdam
Affiliation:
Korteweg-de Vries Institute for Mathematics, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands (e.m.opdam@uva.nl)
Peter E. Trapa
Affiliation:
Department of Mathematics, University of Utah, Salt Lake City, UT 84112, USA (ciubo@math.utah.edu; ptrapa@math.utah.edu)
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Abstract

We define the algebraic Dirac induction map ${\mathrm{Ind} }_{D} $ for graded affine Hecke algebras. The map ${\mathrm{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}^{\ast } $-algebra of a real reductive group using Dirac operators. The definition of ${\mathrm{Ind} }_{D} $ is uniform over the parameter space of the graded affine Hecke algebra. We show that the map ${\mathrm{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 affine Hecke algebra analog of the construction of the discrete series representations of semisimple Lie groups due to Parthasarathy and to Atiyah and Schmid.

Keywords

graded affine Hecke algebra; Dirac index; elliptic representations
Type
Research Article
Information
Journal of the Institute of Mathematics of Jussieu , Volume 13 , Issue 3 , July 2014 , pp. 447 - 486
Copyright
©Cambridge University Press 2013 

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