Spectral mod p Satake isomorphism for GL_n

Abstract

Let $K/\mathbb{Q}_p$ be a finite extension with residue field $k$. By a work of Emerton--Gee, irreducible components inside the reduced special fiber of the moduli stack of rank $n$ étale $(φ,Γ)$-modules are labeled by Serre weights of $\mathrm{GL}_n(k)$. Let $σ$ be a non-Steinberg Serre weight and $\mathcal{C}_σ$ be the corresponding irreducible component. Motivated by the categorical $p$-adic local Langlands program, we construct a natural injective map $\mathcal{O}(\mathcal{C}_σ) \hookrightarrow \mathcal{H}(σ)$ from the ring of global functions on $\mathcal{C}_σ$ to the Hecke algebra of $σ$ compatible with the mod $p$ Satake isomorphism by Herzig and Henniart--Vignéras in a suitable sense. For sufficiently generic $σ$, we prove that it is an isomorphism. As an application, we obtain a natural stratification of the irreducible component whose strata are equipped with a parabolic structure. Our main input is a construction of a morphism from an integral Hecke algebra of a generic tame type to the ring of global functions on a tamely potentially crystalline Emerton--Gee stack.