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Finiteness properties of Subgroups of Houghton Groups of full Hirsch length

Finiteness properties of Subgroups of Houghton Groups of full Hirsch length

来源:Arxiv_logoArxiv
英文摘要

For $n\in \{1,2,3, \ldots\}$, the $n$th Houghton group $H_n$ is the group of those permutations permutations $g$ of the ray set $\{1, \ldots, n\} \times \mathbb{N}$ that are eventually translations along each ray in the sense that there exists $j_0$ depending on $g$ and a vector $(t_1,...,t_n)\in\mathbb{Z}^{n}$ also depending on $g$, such that for all $1\le i\le n$, and all $j\ge j_0$, $$(i,j)g=(i,j+t_i)$$ For all $n\ge 1$, $H_n$ affords an epimorphism to $\mathbb{Z}^{n-1}$ whose kernel is the set of finitary permutations of the ray set. K. S. Brown showed that $H_n$ has type $\operatorname{F}_{n-1}$ but not type $\operatorname{FP}_n$, meaning that $H_n$ has an Eilenberg--MacLane space with finite $(n-1)$-skeleton but does not have an Eilenberg--MacLane with finite $n$-skeleton. We show that, provided $n\ge3$, the same conclusion holds for subgroups $G$ of $H_n$ that are large in the sense that there is an epimorphism $G\twoheadrightarrow\mathbb{Z}^{n-1}$. Our results depend on a generalised form of the Jordan--Wielandt theorem for intransitive permutation groups, as well as a structural analysis of permutational wreath products that allows for distinct chandelier groups associated with distinct orbits when the permutation representation is intransitive.

Charles Cox、Peter Kropholler、Armando Martino

数学

Charles Cox,Peter Kropholler,Armando Martino.Finiteness properties of Subgroups of Houghton Groups of full Hirsch length[EB/OL].(2025-08-11)[2025-08-24].https://arxiv.org/abs/2508.07816.点此复制

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