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Finite groups with a soluble group of coprime automorphisms whose fixed points have bounded Engel sinks
E. I. Khukhroab, P. Shumyatskiic a Sobolev Institute of Mathematics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk
b Charlotte Scott Research Centre for Algebra, Univ. Lincoln, Lincoln, UK
c University of Brasilia
Abstract:
Suppose that a finite group $G$ admits a soluble group of coprime automorphisms $A$. We prove that if, for some positive integer $m$, every element of the centralizer $C_G(A)$ has a left Engel sink of cardinality at most $m$ (or a right Engel sink of cardinality at most $m$), then $G$ has a subgroup of $(|A|,m)$-bounded index which has Fitting height at most $2\alpha (A)+2$, where $\alpha (A)$ is the composition length of $A$. We also prove that if, for some positive integer $r$, every element of the centralizer $C_G(A)$ has a left Engel sink of rank at most $r$ (or a right Engel sink of rank at most $r$), then $G$ has a subgroup of $(|A|,r)$-bounded index which has Fitting height at most $4^{\alpha (A)}+4\alpha (A)+3$. Here, a left Engel sink of an element $g$ of a group $G$ is a set ${\mathscr E}(g)$ such that for every $x\in G$ all sufficiently long commutators $[...[[x,g],g],\dots,g]$ belong to ${\mathscr E}(g)$. (Thus, $g$ is a left Engel element precisely when we can choose ${\mathscr E}(g)=\{ 1\}$.) A right Engel sink of an element $g$ of a group $G$ is a set ${\mathscr R}(g)$ such that for every $x\in G$ all sufficiently long commutators $[...[[g,x],x],\dots,x]$ belong to ${\mathscr R}(g)$. Thus, $g$ is a right Engel element precisely when we can choose ${\mathscr R}(g)=\{ 1\}$.
Keywords:
Engel condition, Fitting subgroup, Fitting height, automorphism.
Received: 28.12.2022 Revised: 30.10.2023
Citation:
E. I. Khukhro, P. Shumyatskii, “Finite groups with a soluble group of coprime automorphisms whose fixed points have bounded Engel sinks”, Algebra Logika, 62:1 (2023), 114–134
Linking options:
https://www.mathnet.ru/eng/al2751 https://www.mathnet.ru/eng/al/v62/i1/p114
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Abstract page: | 74 | Full-text PDF : | 34 | References: | 17 |
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