Links between generalized Montr\'eal-functors

TL;DR

This paper establishes a deep connection between Breuil's pseudocompact $(, abla)$-modules and Schneider-Vigneras' étale hulls, constructing $G$-equivariant maps linking smooth representations to sheaf sections on $G/B$.

Contribution

It demonstrates an isomorphism between Breuil's pseudocompact modules and the basechange of Schneider-Vigneras' étale hulls, and constructs $G$-equivariant maps from dual representations to sheaf sections.

Findings

Isomorphism between Breuil's modules and basechange of Schneider-Vigneras' étale hulls.

Construction of a $G$-equivariant map from $ ext{pi}^ ext{dual}$ to sheaf sections on $G/B$.

Extension of the theory to noncommutative multivariable versions of Breuil's modules.

Abstract

Let $o$ be the ring of integers in a finite extension $K/\mathbb{Q}_p$ and $G=\mathbf{G}(\mathbb{Q}_p)$ be the $\mathbb{Q}_p$-points of a $\mathbb{Q}_p$-split reductive group $\mathbf{G}$ defined over $\mathbb{Z}_p$ with connected centre and split Borel $\mathbf{B}=\mathbf{TN}$. We show that Breuil's pseudocompact $(\varphi,\Gamma)$-module $D^\vee_{\xi}(\pi)$ attached to a smooth $o$-torsion representation $\pi$ of $B=\mathbf{B}(\mathbb{Q}_p)$ is isomorphic to the pseudocompact completion of the basechange $\mathcal{O_E}\otimes_{\Lambda(N_0),\ell}\widetilde{D_{SV}}(\pi)$ to Fontaine's ring (via a Whittaker functional $\ell\colon N_0=\mathbf{N}(\mathbb{Z}_p)\to \mathbb{Z}_p$) of the \'etale hull $\widetilde{D_{SV}}(\pi)$ of $D_{SV}(\pi)$ defined by Schneider and Vigneras. Moreover, we construct a $G$-equivariant map from the Pontryagin dual $\pi^\vee$ to the global sections $\mathfrak{Y}(G/B)$ of the $G$-equivariant sheaf $\mathfrak{Y}$ on $G/B$ attached to a noncommutative multivariable version $D^\vee_{\xi,\ell,\infty}(\pi)$ of Breuil's $D^\vee_{\xi}(\pi)$ whenever $\pi$ comes as the restriction to $B$ of a smooth, admissible representation of $G$ of finite length.