On profinite groups with automorphisms whose fixed points have countable Engel sinks

Abstract

An Engel sink of an element $g$ of a group $G$ is a set $\mathcal{E}(g)$ such that for every $x\in G$ all sufficiently long commutators $[...[[x,g],g],\dots ,g]$ belong to $\mathcal{E}(g)$. (Thus, $g$ is an Engel element precisely when we can choose $\mathcal{E}(g)=\{1\}$.) It is proved that if a profinite group $G$ admits an elementary abelian group of automorphisms $A$ of coprime order $q^2$ for a prime $q$ such that for each $a\in A\setminus \{1\}$ every element of the centralizer $C_G(a)$ has a countable (or finite) Engel sink, then $G$ has a finite normal subgroup $N$ such that $G/N$ is locally nilpotent.

arXiv admin note: text overlap with arXiv:1908.11637, arXiv:2004.11680