Profinite groups with restricted centralizers of $\pi$-elements

TL;DR

This paper investigates profinite groups with restricted centralizers of -elements, showing they have a specific open subgroup structure combining abelian pro- and pro-' subgroups, extending previous results.

Contribution

It establishes that such groups have an open subgroup of the form P  Q, with P abelian pro- and Q pro-'., significantly strengthening earlier findings.

Findings

Profinite groups with restricted -centralizers have a specific subgroup structure.

Such groups contain an open subgroup as a direct product of abelian pro- and pro-' groups.

The result extends previous work by providing a more detailed subgroup decomposition.

Abstract

A group $G$ is said to have restricted centralizers if for each $g$ in $G$ the centralizer $C_G(g)$ either is finite or has finite index in $G$. Shalev showed that a profinite group with restricted centralizers is virtually abelian. Given a set of primes $\pi$, we take interest in profinite groups with restricted centralizers of $\pi$-elements. It is shown that such a profinite group has an open subgroup of the form $P\times Q$, where $P$ is an abelian pro-$\pi$ subgroup and $Q$ is a pro-$\pi'$ subgroup. This significantly strengthens a result from our earlier paper.