Finite generation of iterated wreath products |
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Authors: | Ievgen V Bondarenko |
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Institution: | 1. Mechanics and Mathematics Department, National Taras Shevchenko University of Kyiv, vul.Volodymyrska 64, Kiev, 01033, Ukraine
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Abstract: | Let (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 ${\ldots\wr G_2\wr G_1}Let (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
?\wr G2\wr G1{\ldots\wr G_2\wr G_1} is topologically finitely generated if and only if the profinite abelian group ?n 3 1 Gn/G¢n{\prod_{n\geq 1} G_n/G'_n} is topologically finitely generated. As a corollary, for a finite transitive group G the minimal number of generators of the wreath power
G\wr ?\wr G\wr G{G\wr \ldots\wr G\wr G} (n times) is bounded if G is perfect, and grows linearly if G is non-perfect. As a by-product we construct a finitely generated branch group, which has maximal subgroups of infinite index. |
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Keywords: | |
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