Gelfand-Kirillov dimension for mod $p$ representations of $p$-adic unitary groups of rank 2

TL;DR

This paper establishes the Gelfand-Kirillov dimension for certain mod p representations of rank 2 p-adic unitary groups, linking automorphic forms and Galois representations in a new setting.

Contribution

It proves the Gelfand-Kirillov dimension for specific mod p representations of p-adic unitary groups, extending previous work with new techniques and recent results.

Findings

Gelfand-Kirillov dimension equals the degree of the local field extension.

Connects automorphic forms with Galois representations in the mod p setting.

Uses recent advances in the theory of mod p representations and automorphic forms.

Abstract

Let $p$ be a prime number and $F/F^+$ a CM extension of a totally real field such that every place of $F^+$ above $p$ is unramified and inert in $F$. We fix a finite place $v$ of $F^+$ above $p$, and let $\overline{r}: \textrm{Gal}(\overline{F^+}/F^+) \longrightarrow {}^C\textrm{U}_{1,1}(\overline{\mathbb{F}}_p)$ be a modular $L$-parameter valued in the $C$-group of a rank 2 unitary group associated to $F/F^+$. We assume $\overline{r}$ is semisimple and sufficiently generic at $v$. Using recent results of Breuil--Herzig--Hu--Morra--Schraen along with our previous work, we prove that certain admissible smooth $\overline{\mathbb{F}}_p$-representations of the $p$-adic unitary group $\textrm{U}_{1,1}(F^+_v)$ associated to $\overline{r}$ in spaces of mod $p$ automorphic forms have Gelfand--Kirillov dimension $[F^+_v:\mathbb{Q}_p]$.