Dehn functions of subgroups of products of free groups. Part I: Uniform upper bounds

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Main Authors: Ascari, Dario, Bertolotti, Federica, Italiano, Giovanni, Isenrich, Claudio Llosa, Migliorini, Matteo
Format: Preprint
Published: 2024
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_version_ 1866910812795305984
author Ascari, Dario
Bertolotti, Federica
Italiano, Giovanni
Isenrich, Claudio Llosa
Migliorini, Matteo
author_facet Ascari, Dario
Bertolotti, Federica
Italiano, Giovanni
Isenrich, Claudio Llosa
Migliorini, Matteo
contents Subgroups of direct products of finitely many finitely generated free groups form a natural class that plays an important role in geometric group theory. Its members include fundamental examples, such as the Stallings-Bieri groups. This raises the problem of understanding their geometric invariants. We prove that finitely presented subgroups of direct products of three free groups, as well as subgroups of finiteness type $\mathcal{F}_{n-1}$ in a direct product of $n$ free groups, have Dehn function bounded above by $N^9$. This gives a positive answer to a question of Dison within these important subclasses and provides new insights in the context of Bridson's conjecture stating that finitely presented subgroups of direct products of free groups have polynomially bounded Dehn function. To prove our results we generalise techniques for "pushing fillings" into normal subgroups.
format Preprint
id arxiv_https___arxiv_org_abs_2406_19860
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Dehn functions of subgroups of products of free groups. Part I: Uniform upper bounds
Ascari, Dario
Bertolotti, Federica
Italiano, Giovanni
Isenrich, Claudio Llosa
Migliorini, Matteo
Group Theory
Geometric Topology
20F65 (Primary) 20F05, 20F67, 20F69, 57M07 (Secondary)
Subgroups of direct products of finitely many finitely generated free groups form a natural class that plays an important role in geometric group theory. Its members include fundamental examples, such as the Stallings-Bieri groups. This raises the problem of understanding their geometric invariants. We prove that finitely presented subgroups of direct products of three free groups, as well as subgroups of finiteness type $\mathcal{F}_{n-1}$ in a direct product of $n$ free groups, have Dehn function bounded above by $N^9$. This gives a positive answer to a question of Dison within these important subclasses and provides new insights in the context of Bridson's conjecture stating that finitely presented subgroups of direct products of free groups have polynomially bounded Dehn function. To prove our results we generalise techniques for "pushing fillings" into normal subgroups.
title Dehn functions of subgroups of products of free groups. Part I: Uniform upper bounds
topic Group Theory
Geometric Topology
20F65 (Primary) 20F05, 20F67, 20F69, 57M07 (Secondary)
url https://arxiv.org/abs/2406.19860