Generic and Mod p Kazhdan-Lusztig Theory for GL_2

Abstract

Let $F$ be a non-archimedean local field with residue field $\mathbb{F}_q$ and let $G = GL_{2/F}$. Let $\mathbf{q}$ be an indeterminate and let $H^{(1)}(\mathbf{q})$ be the generic pro-p Iwahori-Hecke algebra of the group $G(F)$. Let $V_{\widehat{G}}$ be the Vinberg monoid of the dual group $\widehat{G}$. We establish a generic version for $H^{(1)}(\mathbf{q})$ of the Kazhdan-Lusztig-Ginzburg spherical representation, the Bernstein map and the Satake isomorphism. We define the flag variety for the monoid $V_{\widehat{G}}$ and establish the characteristic map in its equivariant K-theory. These generic constructions recover the classical ones after the specialization $\mathbf{q} = q \in \mathbb{C}$. At $\mathbf{q} = q = 0 \in\overline{\mathbb{F}}_q$, the spherical map provides a dual parametrization of all the irreducible $H^{(1)}_{\overline{\mathbb{F}}_q}(0)$-modules.