Lubin-Tate moduli space of semisimple mod p Galois representations for GL_2 and Hecke modules

TL;DR

This paper constructs a geometric link between the center of a Hecke algebra for GL_2 over a local field and semisimple Galois representations, extending known morphisms and identifying supersingular modules with Grosse-Kl"onne's bijection.

Contribution

It introduces a scheme parametrizing semisimple Galois representations and constructs a morphism from the Hecke algebra's center to this scheme, generalizing previous results for F=Q_p.

Findings

The morphism from the Hecke algebra's center to the Galois scheme is constructed.

For F=Q_p, the map on supersingular modules matches Grosse-Kl"onne's bijection.

The associated Lubin-Tate (,\u03b3)-modules are explicitly determined.

Abstract

Let $p$ be an odd prime. Let $F$ be a non-archimedean local field of residue characteristic $p$, and let $\mathbb{F}_q$ be its residue field. Let $\mathcal{H}^{(1)}_{\mathbb{F}_q}$ be the pro-$p$-Iwahori-Hecke algebra of the $p$-adic group ${\textrm GL_2}(F)$ with coefficients in $\mathbb{F}_q$, and let $Z(\mathcal{H}^{(1)}_{\mathbb{F}_q})$ be its center. We define a scheme $X(q)_{\mathbb{F}_q}$ whose geometric points parametrize the semisimple two-dimensional Galois representations of ${\textrm Gal}(\overline{F}/F)$ over $\overline{\mathbb{F}}_q$. Then we construct a morphism from the spectrum of $Z(\mathcal{H}^{(1)}_{\mathbb{F}_q})$ to $X(q)_{\mathbb{F}_q}$ generalizing the morphism appearing in \cite{PS2} for $F=\mathbb{Q}_p$. In the case $F/\mathbb{Q}_p$, we show that the induced map from Hecke modules to Galois representations, when restricted to supersingular modules, coincides with Grosse-Kl\"onne's bijection \cite{GK18}. For this, we determine the Lubin-Tate $(\varphi,\Gamma)$-modules associated to absolutely irreducible Galois representations.