English

Finite generation of iterated wreath products

Group Theory 2010-07-02 v2

Abstract

Let (Gn,Xn)(G_n,X_n) be a sequence of finite transitive permutation groups with uniformly bounded number of generators. We prove that the infinitely iterated permutational wreath product ...G2G1...\wr G_2\wr G_1 is topologically finitely generated if and only if the profinite abelian group n1Gn/Gn\prod_{n\geq 1} G_n/G'_n is topologically finitely generated. As a corollary, for a finite transitive group GG the minimal number of generators of the wreath power G...GGG\wr...\wr G\wr G (nn times) is bounded if GG is perfect, and grows linearly if GG is non-perfect. As a by-product we construct a finitely generated branch group, which has maximal subgroups of infinite index, answering [2,Question 14].

Keywords

Cite

@article{arxiv.1002.0320,
  title  = {Finite generation of iterated wreath products},
  author = {Ievgen Bondarenko},
  journal= {arXiv preprint arXiv:1002.0320},
  year   = {2010}
}

Comments

7 pages. An example of a branch group with maximal subgroups of infinite index is added