English

Strong conciseness of coprime commutators in profinite groups

Group Theory 2023-07-28 v2

Abstract

Let GG be a profinite group. The coprime commutators γj\gamma_j^* and δj\delta_j^* are defined as follows. Every element of GG is both a γ1\gamma_1^*-value and a δ0\delta_0^*-value. For j2j\geq 2, let XX be the set of all elements of GG that are powers of γj1\gamma_{j-1}^*-values. An element aa is a γj\gamma_j^*-value if there exist xXx\in X and gGg\in G such that a=[x,g]a=[x,g] and (x,g)=1(|x|,|g|)=1. For j1j\geq 1, let YY be the set of all elements of GG that are powers of δj1\delta_{j-1}^*-values. The element aa is a δj\delta_j^*-value if there exist x,yYx,y\in Y such that a=[x,y]a=[x,y] and (x,y)=1(|x|,|y|)=1. In this paper we establish the following results. A profinite group GG is finite-by-pronilpotent if and only if there is kk such that the set of γk\gamma_k^*-values in GG has cardinality less than 202^{\aleph_0}. A profinite group GG is finite-by-(prosoluble of Fitting height at most kk) if and only if there is kk such that the set of δk\delta_k^*-values in GG has cardinality less than 202^{\aleph_0}.

Keywords

Cite

@article{arxiv.2303.08623,
  title  = {Strong conciseness of coprime commutators in profinite groups},
  author = {Iker de las Heras and Matteo Pintonello and Pavel Shumyatsky},
  journal= {arXiv preprint arXiv:2303.08623},
  year   = {2023}
}