Prosolvable rigidity of surface groups

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Hauptverfasser: Jaikin-Zapirain, Andrei, Morales, Ismael
Format: Preprint
Veröffentlicht: 2023
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author Jaikin-Zapirain, Andrei
Morales, Ismael
author_facet Jaikin-Zapirain, Andrei
Morales, Ismael
contents Surface groups are known to be the Poincaré Duality groups of dimension two since the work of Eckmann, Linnell and Müller. We prove a prosolvable analogue of this result that allows us to show that surface groups are profinitely (and prosolvably) rigid among finitely generated groups that satisfy $\mathrm{cd}(G)=2$ and $b_2^{(2)}(G)=0$. We explore two other consequences. On the one hand, we derive that if $u$ is a surface word of a finitely generated free group $F$ and $v\in F$ is measure equivalent to $u$ in all finite solvable quotients of $F$ then $u$ and $v$ belong to the same $\mathrm{Aut}(F)$-orbit. Finally, we get a partial result towards Mel'nikov's surface group conjecture. Let $F$ be a free group of rank $n\geq 3$ and let $w\in F$. Suppose that $G=F/\langle\!\langle w\rangle\!\rangle$ is a residually finite group all of whose finite-index subgroups are one-relator groups. Then $G$ is 2-free. Moreover, we show that if $H^2(G; \mathbb{Z})\neq 0$ then $G$ must be a surface group.
format Preprint
id arxiv_https___arxiv_org_abs_2312_12293
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Prosolvable rigidity of surface groups
Jaikin-Zapirain, Andrei
Morales, Ismael
Group Theory
20J06, 20E18 (Primary), 16K40, 20C07 (Secondary)
Surface groups are known to be the Poincaré Duality groups of dimension two since the work of Eckmann, Linnell and Müller. We prove a prosolvable analogue of this result that allows us to show that surface groups are profinitely (and prosolvably) rigid among finitely generated groups that satisfy $\mathrm{cd}(G)=2$ and $b_2^{(2)}(G)=0$. We explore two other consequences. On the one hand, we derive that if $u$ is a surface word of a finitely generated free group $F$ and $v\in F$ is measure equivalent to $u$ in all finite solvable quotients of $F$ then $u$ and $v$ belong to the same $\mathrm{Aut}(F)$-orbit. Finally, we get a partial result towards Mel'nikov's surface group conjecture. Let $F$ be a free group of rank $n\geq 3$ and let $w\in F$. Suppose that $G=F/\langle\!\langle w\rangle\!\rangle$ is a residually finite group all of whose finite-index subgroups are one-relator groups. Then $G$ is 2-free. Moreover, we show that if $H^2(G; \mathbb{Z})\neq 0$ then $G$ must be a surface group.
title Prosolvable rigidity of surface groups
topic Group Theory
20J06, 20E18 (Primary), 16K40, 20C07 (Secondary)
url https://arxiv.org/abs/2312.12293