Non-closed subgroups of weakly branch groups
Group Theory
2025-11-20 v1
Abstract
For a weakly branch group acting on a regular enough rooted tree, we provide two constructions of continuous families of distinct subgroups that are not closed in the profinite topology on . On the one hand, we construct a continuous family of distinct non-closed subgroups such that each in the family is not ERF, that is, contains subgroups not closed in the profinite topology on . On the other hand, under an additional assumption on , we construct a continuous family of ERF subgroups which are not closed in the congruence (and in the profinite) topology on .
Cite
@article{arxiv.2511.15277,
title = {Non-closed subgroups of weakly branch groups},
author = {Jorge Fariña-Asategui and Paul-Henry Leemann and Tatiana Nagnibeda},
journal= {arXiv preprint arXiv:2511.15277},
year = {2025}
}
Comments
11 pages