English

Profinite groups with an automorphism of prime order whose fixed points have finite Engel sinks

Group Theory 2021-01-12 v1

Abstract

A right Engel sink of an element gg of a group GG is a set R(g){\mathscr R}(g) such that for every xGx\in G all sufficiently long commutators [...[[g,x],x],,x][...[[g,x],x],\dots ,x] belong to R(g){\mathscr R}(g). (Thus, gg is a right Engel element precisely when we can choose R(g)={1}{\mathscr R}(g)=\{ 1\}.) We prove that if a profinite group GG admits a coprime automorphism φ\varphi of prime order such that every fixed point of φ\varphi has a finite right Engel sink, then GG has an open locally nilpotent subgroup. A left Engel sink of an element gg of a group GG is a 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). (Thus, gg is a left Engel element precisely when we can choose E(g)={1}{\mathscr E}(g)=\{ 1\}.) We prove that if a profinite group GG admits a coprime automorphism φ\varphi of prime order such that every fixed point of φ\varphi has a finite left Engel sink, then GG has an open pronilpotent-by-nilpotent subgroup.

Keywords

Cite

@article{arxiv.2101.03404,
  title  = {Profinite groups with an automorphism of prime order whose fixed points have finite Engel sinks},
  author = {E. I. Khukhro and P. Shumyatsky},
  journal= {arXiv preprint arXiv:2101.03404},
  year   = {2021}
}