Subgroups with all finite lifts isomorphic are conjugate

Fuente: arXiv
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Auteurs principaux: Karshon, Ido, Lubotzky, Alexander, McReynolds, D. B., Reid, Alan W., Shusterman, Mark
Format: Preprint
Publié: 2026
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author Karshon, Ido
Lubotzky, Alexander
McReynolds, D. B.
Reid, Alan W.
Shusterman, Mark
author_facet Karshon, Ido
Lubotzky, Alexander
McReynolds, D. B.
Reid, Alan W.
Shusterman, Mark
contents We show that for non-conjugate subgroups $G_1$ and $G_2$ of a finite group $G$ there exists an extension of $G$ (by a finite group) in which the pre-images of $G_1$ and $G_2$ are not isomorphic. This allows us to show that $\mathbb Z$-coset equivalent subgroups of a finite group are not necessarily isomorphic, answering a question of Dipendra Prasad. We also indicate connections to profinite rigidity, anabelian geometry, mapping class groups, and non-arithmetic lattices in Lie groups.
format Preprint
id arxiv_https___arxiv_org_abs_2602_15463
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Subgroups with all finite lifts isomorphic are conjugate
Karshon, Ido
Lubotzky, Alexander
McReynolds, D. B.
Reid, Alan W.
Shusterman, Mark
Group Theory
Algebraic Geometry
Geometric Topology
Number Theory
We show that for non-conjugate subgroups $G_1$ and $G_2$ of a finite group $G$ there exists an extension of $G$ (by a finite group) in which the pre-images of $G_1$ and $G_2$ are not isomorphic. This allows us to show that $\mathbb Z$-coset equivalent subgroups of a finite group are not necessarily isomorphic, answering a question of Dipendra Prasad. We also indicate connections to profinite rigidity, anabelian geometry, mapping class groups, and non-arithmetic lattices in Lie groups.
title Subgroups with all finite lifts isomorphic are conjugate
topic Group Theory
Algebraic Geometry
Geometric Topology
Number Theory
url https://arxiv.org/abs/2602.15463