Nonunital prime rings graded by ordered groups

Fuente: arXiv
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Main Authors: Lännström, Daniel, Lundström, Patrik, Öinert, Johan, Wagner, Stefan
Format: Preprint
Published: 2025
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author Lännström, Daniel
Lundström, Patrik
Öinert, Johan
Wagner, Stefan
author_facet Lännström, Daniel
Lundström, Patrik
Öinert, Johan
Wagner, Stefan
contents Let $G$ be a group with identity element $e$, and suppose that $S$ is an associative $G$-graded ring that is not necessarily unital. In the case where $G$ is an ordered group, we show that a graded ideal is prime if and only if it is graded prime. Consequently, in that setting, a graded ring is prime if and only if it is graded prime. For any group $G$, if $S$ is what we call ideally symmetrically $G$-graded, then we show that there is a bijective correspondence between the $G$-graded prime ideals of $S$ and the $G$-prime ideals of $S_e$. We use this correspondence in the case where $G$ is ordered and $S$ is ideally symmetrically $G$-graded to show that $S$ is prime if and only if $S_e$ is $G$-prime. These results generalize classical theorems by Năstăsescu and Van Oystaeyen to a nonunital setting. As applications, we provide a new proof of a primeness criterion for Leavitt path rings and establish conditions for primeness of symmetrically $G$-graded subrings of group rings over fully idempotent rings.
format Preprint
id arxiv_https___arxiv_org_abs_2510_26734
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Nonunital prime rings graded by ordered groups
Lännström, Daniel
Lundström, Patrik
Öinert, Johan
Wagner, Stefan
Rings and Algebras
16D25, 16D80, 16W50, 16N60, 16S88, 16S35
Let $G$ be a group with identity element $e$, and suppose that $S$ is an associative $G$-graded ring that is not necessarily unital. In the case where $G$ is an ordered group, we show that a graded ideal is prime if and only if it is graded prime. Consequently, in that setting, a graded ring is prime if and only if it is graded prime. For any group $G$, if $S$ is what we call ideally symmetrically $G$-graded, then we show that there is a bijective correspondence between the $G$-graded prime ideals of $S$ and the $G$-prime ideals of $S_e$. We use this correspondence in the case where $G$ is ordered and $S$ is ideally symmetrically $G$-graded to show that $S$ is prime if and only if $S_e$ is $G$-prime. These results generalize classical theorems by Năstăsescu and Van Oystaeyen to a nonunital setting. As applications, we provide a new proof of a primeness criterion for Leavitt path rings and establish conditions for primeness of symmetrically $G$-graded subrings of group rings over fully idempotent rings.
title Nonunital prime rings graded by ordered groups
topic Rings and Algebras
16D25, 16D80, 16W50, 16N60, 16S88, 16S35
url https://arxiv.org/abs/2510.26734