English

$p$-Basilica groups

Group Theory 2021-05-27 v1

Abstract

We consider a generalisation of the Basilica group to all odd primes: the pp-Basilica groups acting on the pp-adic tree. We show that the pp-Basilica groups have the pp-congruence subgroup property but not the congruence subgroup property nor the weak congruence subgroup property. This provides the first examples of weakly branch groups with such properties. In addition, the pp-Basilica groups give the first examples of weakly branch, but not branch, groups which are super strongly fractal. We compute the orders of the congruence quotients of these groups, which enable us to determine the Hausdorff dimensions of the pp-Basilica groups. Lastly, we show that the pp-Basilica groups do not possess maximal subgroups of infinite index and that they have infinitely many non-normal maximal subgroups.

Keywords

Cite

@article{arxiv.2105.12443,
  title  = {$p$-Basilica groups},
  author = {Elena Di Domenico and Gustavo A. Fernández-Alcober and Marialaura Noce and Anitha Thillaisundaram},
  journal= {arXiv preprint arXiv:2105.12443},
  year   = {2021}
}

Comments

20 pages

R2 v1 2026-06-24T02:28:50.053Z