On modular rigidity for ${\rm GL}_n$

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Main Authors: Matringe, Nadir, Mínguez, Alberto, Sécherre, Vincent
Format: Preprint
Published: 2024
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_version_ 1866910617558843392
author Matringe, Nadir
Mínguez, Alberto
Sécherre, Vincent
author_facet Matringe, Nadir
Mínguez, Alberto
Sécherre, Vincent
contents Let $k$ be a global field and $\mathbb{A}_k$ be its ring of adeles. Let $\ell$ be a prime number and fix a field isomorphism from $\mathbb{C}$ to $\overline{\mathbb{Q}}_{\ell}$. Let $Π_1$ and $Π_2$ be cuspidal automorphic representations of ${\rm GL}_n(\mathbb{A}_k)$ for some integer $n\geq1$. In this paper, we study the following question: assuming that there is a finite set $S$ of places of $k$ containing all Archimedean places and all finite places above $\ell$ such that, for all $v\notin S$, the local components $Π_{1,v} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ and $Π_{2,v} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ are unramified and their Satake parameters are congruent mod $\ell$, are the local components $Π_{1,w} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ and $Π_{2,w} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ integral, and do their reductions mod $\ell$ share an irreducible factor for all non-Archimedean places $w$ not dividing $\ell$? We show that, under certain conditions on $Π_1$ and $Π_2$, the answer is yes. We also give a simple proof when $k$ is a function field.
format Preprint
id arxiv_https___arxiv_org_abs_2409_15209
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On modular rigidity for ${\rm GL}_n$
Matringe, Nadir
Mínguez, Alberto
Sécherre, Vincent
Representation Theory
11F70
Let $k$ be a global field and $\mathbb{A}_k$ be its ring of adeles. Let $\ell$ be a prime number and fix a field isomorphism from $\mathbb{C}$ to $\overline{\mathbb{Q}}_{\ell}$. Let $Π_1$ and $Π_2$ be cuspidal automorphic representations of ${\rm GL}_n(\mathbb{A}_k)$ for some integer $n\geq1$. In this paper, we study the following question: assuming that there is a finite set $S$ of places of $k$ containing all Archimedean places and all finite places above $\ell$ such that, for all $v\notin S$, the local components $Π_{1,v} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ and $Π_{2,v} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ are unramified and their Satake parameters are congruent mod $\ell$, are the local components $Π_{1,w} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ and $Π_{2,w} \otimes_{\mathbb{C}} \overline{\mathbb{Q}}_{\ell}$ integral, and do their reductions mod $\ell$ share an irreducible factor for all non-Archimedean places $w$ not dividing $\ell$? We show that, under certain conditions on $Π_1$ and $Π_2$, the answer is yes. We also give a simple proof when $k$ is a function field.
title On modular rigidity for ${\rm GL}_n$
topic Representation Theory
11F70
url https://arxiv.org/abs/2409.15209