English

On small profinite groups

Group Theory 2015-12-29 v2 Logic

Abstract

A profinite group is called small if it has only finitely many open subgroups of index n for each positive integer n. We show that every Frattini cover of a small profinite group is small. A profinite group is called strongly complete if every subgroup of finite index is open. We show that two profinite groups that are elementarily equivalent, in the first-order language of groups, are isomorphic if one of them is strongly complete, extending a result of Moshe Jarden and Alexander Lubotzky which treats the case of finitely generated profinite groups.

Keywords

Cite

@article{arxiv.1511.08760,
  title  = {On small profinite groups},
  author = {Patrick Helbig},
  journal= {arXiv preprint arXiv:1511.08760},
  year   = {2015}
}

Comments

Previously titled "Small profinite groups and their elementary theory"; extended Question 3.15

R2 v1 2026-06-22T11:55:47.252Z