English

Compact groups with probabilistically central monothetic subgroups

Group Theory 2022-12-19 v3

Abstract

If KK is a closed subgroup of a compact group GG, the probability that randomly chosen pair of elements from KK and GG commute is denoted by Pr(K,G)Pr(K,G). Say that a subgroup KGK\leq G is ϵ\epsilon-central in GG if Pr(g,G)ϵPr(\langle g \rangle,G)\geq \epsilon for any gg in KK. Here g\langle g \rangle denotes the monothetic subgroup generated by gGg\in G. Our main result is that if KK is ϵ\epsilon-central in GG, then there is an ϵ\epsilon-bounded number ee and a normal subgroup TGT\leq G such that the index [G:T][G:T] and the order of the commutator subgroup [Ke,T][K^e,T] both are finite and ϵ\epsilon-bounded. In particular, if GG is a compact group for which there is ϵ>0\epsilon>0 such that Pr(g,G)ϵPr(\langle g \rangle,G)\geq \epsilon for any gGg \in G, then there is an ϵ\epsilon-bounded number ee and a normal subgroup TT such that the index [G:T][G:T] and the order of [Ge,T][G^e,T] both are finite and ϵ\epsilon-bounded.

Keywords

Cite

@article{arxiv.2110.00049,
  title  = {Compact groups with probabilistically central monothetic subgroups},
  author = {João Azevedo and Pavel Shumyatsky},
  journal= {arXiv preprint arXiv:2110.00049},
  year   = {2022}
}

Comments

Changes following referee's suggestions. Final version, accepted in Israel J. of Math

R2 v1 2026-06-24T06:32:15.207Z