The second integral homology of ${\rm SL}_2(\mathbb{Z}[1/n])$

Fuente: arXiv
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Main Authors: Mirzaii, Behrooz, Ramos, Bruno Reis, Verissimo, Thiago
Format: Preprint
Published: 2025
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author Mirzaii, Behrooz
Ramos, Bruno Reis
Verissimo, Thiago
author_facet Mirzaii, Behrooz
Ramos, Bruno Reis
Verissimo, Thiago
contents In this article, we explore the second integral homology, or Schur multiplier, of the special linear group ${\rm SL}_2(\mathbb{Z}[1/n])$ for a positive integer $n$. We definitively calculate the group structure of $H_2({\rm SL}_2(\mathbb{Z}[1/n]),\mathbb{Z})$ when $n$ is divisible by one of the primes $2$, $3$, $5$, $7$ or $13$. For a general $n > 1$, we offer a partial description by placing the homology group within an exact sequence, and we investigate its rank. Finally, we propose a conjectural structure for $H_2({\rm SL}_2(\mathbb{Z}[1/n]),\mathbb{Z})$ when $n$ is not divisible by any of those specific primes.
format Preprint
id arxiv_https___arxiv_org_abs_2503_12190
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The second integral homology of ${\rm SL}_2(\mathbb{Z}[1/n])$
Mirzaii, Behrooz
Ramos, Bruno Reis
Verissimo, Thiago
K-Theory and Homology
19G99 19G99, 20G10,
In this article, we explore the second integral homology, or Schur multiplier, of the special linear group ${\rm SL}_2(\mathbb{Z}[1/n])$ for a positive integer $n$. We definitively calculate the group structure of $H_2({\rm SL}_2(\mathbb{Z}[1/n]),\mathbb{Z})$ when $n$ is divisible by one of the primes $2$, $3$, $5$, $7$ or $13$. For a general $n > 1$, we offer a partial description by placing the homology group within an exact sequence, and we investigate its rank. Finally, we propose a conjectural structure for $H_2({\rm SL}_2(\mathbb{Z}[1/n]),\mathbb{Z})$ when $n$ is not divisible by any of those specific primes.
title The second integral homology of ${\rm SL}_2(\mathbb{Z}[1/n])$
topic K-Theory and Homology
19G99 19G99, 20G10,
url https://arxiv.org/abs/2503.12190