Symmetric modules over the infinite polynomial ring I: nilpotent quotients

Fuente: arXiv
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Main Authors: Nagpal, Rohit, Snowden, Andrew, Yu, Teresa
Format: Preprint
Published: 2025
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author Nagpal, Rohit
Snowden, Andrew
Yu, Teresa
author_facet Nagpal, Rohit
Snowden, Andrew
Yu, Teresa
contents Cohen proved that the infinite variable polynomial ring $R=k[x_1,x_2,\ldots]$ is noetherian with respect to the action of the infinite symmetric group $\mathfrak{S}$. The first two authors began a program to understand the $\mathfrak{S}$-equivariant algebra of $R$ in detail. In previous work, they classified the $\mathfrak{S}$-prime ideals of $R$. An important example of an $\mathfrak{S}$-prime is the ideal $\mathfrak{h}_s$ generated by $(s+1)$st powers of the variables. In this paper, we study the category of $R/\mathfrak{h}_s$-modules. We obtain a number of results, and mention just three here: (a) we determine the Grothendieck group of the category; (b) we show that the Krull--Gabriel dimension is $s$; and (c) we obtain generators for the derived category. This paper will play a key role in subsequent work where we study general modules.
format Preprint
id arxiv_https___arxiv_org_abs_2508_04624
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Symmetric modules over the infinite polynomial ring I: nilpotent quotients
Nagpal, Rohit
Snowden, Andrew
Yu, Teresa
Commutative Algebra
Representation Theory
Cohen proved that the infinite variable polynomial ring $R=k[x_1,x_2,\ldots]$ is noetherian with respect to the action of the infinite symmetric group $\mathfrak{S}$. The first two authors began a program to understand the $\mathfrak{S}$-equivariant algebra of $R$ in detail. In previous work, they classified the $\mathfrak{S}$-prime ideals of $R$. An important example of an $\mathfrak{S}$-prime is the ideal $\mathfrak{h}_s$ generated by $(s+1)$st powers of the variables. In this paper, we study the category of $R/\mathfrak{h}_s$-modules. We obtain a number of results, and mention just three here: (a) we determine the Grothendieck group of the category; (b) we show that the Krull--Gabriel dimension is $s$; and (c) we obtain generators for the derived category. This paper will play a key role in subsequent work where we study general modules.
title Symmetric modules over the infinite polynomial ring I: nilpotent quotients
topic Commutative Algebra
Representation Theory
url https://arxiv.org/abs/2508.04624