Model-theoretic $K_1$ for modules over semisimple rings: (weak) Morita invariance

Fuente: arXiv
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Main Authors: Banerjee, Sourayan, Kuber, Amit
Format: Preprint
Published: 2025
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author Banerjee, Sourayan
Kuber, Amit
author_facet Banerjee, Sourayan
Kuber, Amit
contents This paper is a sequel to a paper by the same authors, where they defined $K$-groups of model-theoretic structures, and computed $K_1$ of free modules over PIDs. In this paper, we compute $K_1$ of a right $M_q(R)$-module $M$, where $R$ is a division ring, $q\geq1$, and $|M_q(R)|\neq 2$. As a consequence, we obtain a (weak) Morita invariance $K_1(R_R)\cong K_1((M_q(R))_{M_q(R)})$ for all division rings $R$ and $q\geq 1$. Finally, we compute $K_1$ of a module over a semisimple ring by showing that the model-theoretic $K_1$ commutes with finite product of modules. We also show that the algebraic $K_1$ of a finite product of infinite matrix rings embeds into the model-theoretic $K_1$ of their right regular modules.
format Preprint
id arxiv_https___arxiv_org_abs_2511_05180
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Model-theoretic $K_1$ for modules over semisimple rings: (weak) Morita invariance
Banerjee, Sourayan
Kuber, Amit
Logic
K-Theory and Homology
03C60, 19B99, 19B14
This paper is a sequel to a paper by the same authors, where they defined $K$-groups of model-theoretic structures, and computed $K_1$ of free modules over PIDs. In this paper, we compute $K_1$ of a right $M_q(R)$-module $M$, where $R$ is a division ring, $q\geq1$, and $|M_q(R)|\neq 2$. As a consequence, we obtain a (weak) Morita invariance $K_1(R_R)\cong K_1((M_q(R))_{M_q(R)})$ for all division rings $R$ and $q\geq 1$. Finally, we compute $K_1$ of a module over a semisimple ring by showing that the model-theoretic $K_1$ commutes with finite product of modules. We also show that the algebraic $K_1$ of a finite product of infinite matrix rings embeds into the model-theoretic $K_1$ of their right regular modules.
title Model-theoretic $K_1$ for modules over semisimple rings: (weak) Morita invariance
topic Logic
K-Theory and Homology
03C60, 19B99, 19B14
url https://arxiv.org/abs/2511.05180