English

Almost Engel compact groups

Group Theory 2017-05-16 v2

Abstract

We say that a group GG is almost Engel if for every gGg\in G there is a finite set E(g){\mathscr E}(g) such that for every xGx\in G all sufficiently long commutators [...[[x,g],g],,g][...[[x,g],g],\dots ,g] belong to E(g){\mathscr E}(g), that is, for every xGx\in G there is a positive integer n(x,g)n(x,g) such that [...[[x,g],g],,g]E(g)[...[[x,g],g],\dots ,g]\in {\mathscr E}(g) if gg is repeated at least n(x,g)n(x,g) times. (Thus, Engel groups are precisely the almost Engel groups for which we can choose E(g)={1}{\mathscr E}(g)=\{ 1\} for all gGg\in G.) We prove that if a compact (Hausdorff) group GG is almost Engel, then GG has a finite normal subgroup NN such that G/NG/N is locally nilpotent. If in addition there is a uniform bound E(g)m|{\mathscr E}(g)|\leq m for the orders of the corresponding sets, then the subgroup NN can be chosen of order bounded in terms of mm. The proofs use the Wilson--Zelmanov theorem saying that Engel profinite groups are locally nilpotent.

Keywords

Cite

@article{arxiv.1610.02079,
  title  = {Almost Engel compact groups},
  author = {E. I. Khukhro and P. Shumyatsky},
  journal= {arXiv preprint arXiv:1610.02079},
  year   = {2017}
}

Comments

A few minor corrections. arXiv admin note: substantial text overlap with arXiv:1512.06097

R2 v1 2026-06-22T16:13:44.201Z