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
Аннотация:
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.
Ключевые слова:
growth of groups, intermediate growth, Grigorchuk group, growth bounds.
MSC: 20E08 Поступила в редакцию: 06.09.2019
Исправленный вариант: 30.06.2020
Язык публикации: английский
DOI:
10.12958/adm1451