Algebres de Hecke affines generiques

Abstract

Let $H$ be a generic affine Hecke algebra (Iwahori-Matsumoto definition) over a polynomial algebra with a finite number of indeterminates over the ring of integers. We prove the existence of an integral Bernstein-Lusztig basis related to the Iwahori-Matsumoto basis by a strictly upper triangular matrix, from which we deduce that the center $Z$ of $H$ is finitely generated and that $H$ is a finite type $Z$-module (this was proved after inversion of the parameters by Bernstein-Lusztig), and we give some applications to the theory of $H$-modules where the parameters act by 0. These results are related to the smooth $p$-adic or mod $p$ representations of reductive $p$-adic groups. We introduce the supersingular modules of the affine Hecke algebra of GL(n) with parameter 0, probably analogues of the Barthel-Livne supersingular mod $p$ representations of GL(2).