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Autores principales: Ern, Thang Pang, Xi, Malcolm Tan Jun
Formato: Preprint
Publicado: 2025
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Acceso en línea:https://arxiv.org/abs/2506.19812
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author Ern, Thang Pang
Xi, Malcolm Tan Jun
author_facet Ern, Thang Pang
Xi, Malcolm Tan Jun
contents We show that the symmetry of \[f\left(a,b\right)=\frac{\operatorname{gcd}\left(ab,a+b\right)}{\operatorname{gcd}\left(a,b\right)}\] stems from an $\operatorname{SL}_2\left(\mathbb{Z}\right)$ action on primitive pairs and that all solutions to $f\left(a,b\right)=n$ admit a uniform three-parameter description -- recovering arithmetic-progression families via the Chinese remainder theorem when $n$ is squarefree. It shows that the density of pairs with $f\left(a,b\right)=1$ tends to $\prod_p\left(1-p^{-2}(p+1)^{-1}\right)\approx0.88151$, and that its higher-order analogue $f_r$ has a limiting density $6/π^2$ for $r\ge2$.
format Preprint
id arxiv_https___arxiv_org_abs_2506_19812
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Asymptotic Density of a GCD-based Map
Ern, Thang Pang
Xi, Malcolm Tan Jun
Number Theory
We show that the symmetry of \[f\left(a,b\right)=\frac{\operatorname{gcd}\left(ab,a+b\right)}{\operatorname{gcd}\left(a,b\right)}\] stems from an $\operatorname{SL}_2\left(\mathbb{Z}\right)$ action on primitive pairs and that all solutions to $f\left(a,b\right)=n$ admit a uniform three-parameter description -- recovering arithmetic-progression families via the Chinese remainder theorem when $n$ is squarefree. It shows that the density of pairs with $f\left(a,b\right)=1$ tends to $\prod_p\left(1-p^{-2}(p+1)^{-1}\right)\approx0.88151$, and that its higher-order analogue $f_r$ has a limiting density $6/π^2$ for $r\ge2$.
title On the Asymptotic Density of a GCD-based Map
topic Number Theory
url https://arxiv.org/abs/2506.19812