Clebsch-Gordan and the theta filtration for modular representations of $\mathrm{GL}_2({\mathbb F}_q)$

Fuente: arXiv
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Autores principales: Bhattacharjee, Srijeet, Ghate, Eknath, Pandey, Shivansh, Veerapaneni, Sriram
Formato: Preprint
Publicado: 2025
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author Bhattacharjee, Srijeet
Ghate, Eknath
Pandey, Shivansh
Veerapaneni, Sriram
author_facet Bhattacharjee, Srijeet
Ghate, Eknath
Pandey, Shivansh
Veerapaneni, Sriram
contents Let $p$ be a prime. We solve two problems in the mod $p$ representation theory of $\mathrm{GL}_2(\mathbb{F}_{q})$ where $q=p^f$. We first prove a Clebsch-Gordan decomposition theorem for the tensor product of two mod $p$ representations of $\mathrm{GL}_2(\mathbb{F}_{q})$. As an application, we use this to guess the structure of quotients of symmetric power representations of $\mathrm{GL}_2(\mathbb{F}_{q})$ by submodules in the theta filtration. We then give a direct proof of this structure showing that such quotients are built out of principal series representations.
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publishDate 2025
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spellingShingle Clebsch-Gordan and the theta filtration for modular representations of $\mathrm{GL}_2({\mathbb F}_q)$
Bhattacharjee, Srijeet
Ghate, Eknath
Pandey, Shivansh
Veerapaneni, Sriram
Representation Theory
Number Theory
Let $p$ be a prime. We solve two problems in the mod $p$ representation theory of $\mathrm{GL}_2(\mathbb{F}_{q})$ where $q=p^f$. We first prove a Clebsch-Gordan decomposition theorem for the tensor product of two mod $p$ representations of $\mathrm{GL}_2(\mathbb{F}_{q})$. As an application, we use this to guess the structure of quotients of symmetric power representations of $\mathrm{GL}_2(\mathbb{F}_{q})$ by submodules in the theta filtration. We then give a direct proof of this structure showing that such quotients are built out of principal series representations.
title Clebsch-Gordan and the theta filtration for modular representations of $\mathrm{GL}_2({\mathbb F}_q)$
topic Representation Theory
Number Theory
url https://arxiv.org/abs/2511.02299