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RESEARCH ARTICLE
On growth of generalized Grigorchuk's overgroups
S. T. Samarakoon Department of Mathematics, Mailstop 3368, Texas A&M University, College Station, TX 77843-3368, United States
Abstract:
Grigorchuk's Overgroup $\widetilde{\mathcal{G}}$, is a branch group of intermediate growth. It contains the first Grigorchuk's torsion group $\mathcal{G}$ of intermediate growth constructed in 1980, but also has elements of infinite order. Its growth is substantially greater than the growth of $\mathcal{G}$. The group $\mathcal{G}$, corresponding to the sequence $(012)^\infty = 012012 \cdots$, is a member of the family $\{ G_\omega | \omega \in \Omega = \{ 0, 1, 2 \}^\mathbb{N} \}$ consisting of groups of intermediate growth when sequence $\omega$ is not eventually constant. Following this construction, we define the family $\{ \widetilde{G}_\omega, \omega \in \Omega \}$ of generalized overgroups. Then $\widetilde{\mathcal{G}} = \widetilde{G}_{(012)^\infty}$ and $G_\omega$ is a subgroup of $\widetilde{G}_\omega$ for each $\omega \in \Omega$. We prove, if $\omega$ is eventually constant, then $\widetilde{G}_\omega$ is of polynomial growth and if $\omega$ is not eventually constant, then $\widetilde{G}_\omega$ is of intermediate growth.
Keywords:
growth of groups, intermediate growth, Grigorchuk group, growth bounds.
Received: 06.09.2019 Revised: 30.06.2020
Citation:
S. T. Samarakoon, “On growth of generalized Grigorchuk's overgroups”, Algebra Discrete Math., 30:1 (2020), 97–117
Linking options:
https://www.mathnet.ru/eng/adm768 https://www.mathnet.ru/eng/adm/v30/i1/p97
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Abstract page: | 56 | Full-text PDF : | 25 | References: | 19 |
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