Finiteness properties of Subgroups of Houghton Groups of full Hirsch length
Finiteness properties of Subgroups of Houghton Groups of full Hirsch length
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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