Filtrations and Growth of $\mathbb G$-modules

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1. Verfasser: Friedlander, Eric M.
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Veröffentlicht: 2023
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author Friedlander, Eric M.
author_facet Friedlander, Eric M.
contents We investigate infinite dimensional modules for an affine group scheme $\mathbb G$ of finite type over a field of positive characteristic $p$. For any subspace $X \subset \mathcal O(\mathbb G)$ of the coordinate algebra of $\mathbb G$, we consider the abelian subcategory $Mod(\mathbb G,X) \subset Mod(\mathbb G)$ of ``$X$-comodules" and the left exact functor $(-)_X: Mod(\mathbb G) \to Mod(\mathbb G,X)$ which is right adjoint to the inclusion functor. We employ ``ascending converging sequences" $\{ X_i \}$ of subspaces of $\mathcal O(\mathbb G)$ to provide functorial filtrations $\{ M_{X_i }\}$ of each $\mathbb G$-module $M$. A $\mathbb G$-module $M$ is injective if and only if each $M_{X_i}$ is an injective $X_i$-comodule for some (or, equivalently, for all) such $\{ X_i \}$. We consider the explicit ascending converging sequence $ \{ \mathcal O(\mathbb G)_{\leq d,ϕ} \}$ of finite dimensional subcoalgebras of $\mathcal O(\mathbb G)$ depending upon a closed embedding $ϕ: \mathbb G \ \hookrightarrow \ GL_N$. Of particular interest to us are mock injective $\mathbb G$-modules, modules whose support varieties are empty. Restrictions of a $\mathbb G$-module to each $\mathcal O(\mathbb G)_{\leq d,ϕ}$ provide new invariants for $\mathbb G$-modules. For cofinite $\mathbb G$-modules $M$, we explore the the growth of $d \mapsto M_{\cal O(\mathbb G)_{\leq d,ϕ}}$.
format Preprint
id arxiv_https___arxiv_org_abs_2305_10921
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Filtrations and Growth of $\mathbb G$-modules
Friedlander, Eric M.
Representation Theory
20G05, 20C20, 20G10
We investigate infinite dimensional modules for an affine group scheme $\mathbb G$ of finite type over a field of positive characteristic $p$. For any subspace $X \subset \mathcal O(\mathbb G)$ of the coordinate algebra of $\mathbb G$, we consider the abelian subcategory $Mod(\mathbb G,X) \subset Mod(\mathbb G)$ of ``$X$-comodules" and the left exact functor $(-)_X: Mod(\mathbb G) \to Mod(\mathbb G,X)$ which is right adjoint to the inclusion functor. We employ ``ascending converging sequences" $\{ X_i \}$ of subspaces of $\mathcal O(\mathbb G)$ to provide functorial filtrations $\{ M_{X_i }\}$ of each $\mathbb G$-module $M$. A $\mathbb G$-module $M$ is injective if and only if each $M_{X_i}$ is an injective $X_i$-comodule for some (or, equivalently, for all) such $\{ X_i \}$. We consider the explicit ascending converging sequence $ \{ \mathcal O(\mathbb G)_{\leq d,ϕ} \}$ of finite dimensional subcoalgebras of $\mathcal O(\mathbb G)$ depending upon a closed embedding $ϕ: \mathbb G \ \hookrightarrow \ GL_N$. Of particular interest to us are mock injective $\mathbb G$-modules, modules whose support varieties are empty. Restrictions of a $\mathbb G$-module to each $\mathcal O(\mathbb G)_{\leq d,ϕ}$ provide new invariants for $\mathbb G$-modules. For cofinite $\mathbb G$-modules $M$, we explore the the growth of $d \mapsto M_{\cal O(\mathbb G)_{\leq d,ϕ}}$.
title Filtrations and Growth of $\mathbb G$-modules
topic Representation Theory
20G05, 20C20, 20G10
url https://arxiv.org/abs/2305.10921