Glasner property for unipotently generated group actions on tori
A theorem of Glasner from 1979 shows that if $A \subset \mathbb{T} = \mathbb{R}/\mathbb{Z}$ is infinite then for each $\epsilon > 0$ there exists an integer $n$ such that $nA$ is $\epsilon$-dense and Berend-Peres later showed that in fact one can take $n$ to be of the form $f(m)$ for any non-cons...
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| Main Authors | , |
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| Format | Journal Article |
| Language | English |
| Published |
16.03.2021
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| Subjects | |
| Online Access | Get full text |
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| Summary: | A theorem of Glasner from 1979 shows that if $A \subset \mathbb{T} =
\mathbb{R}/\mathbb{Z}$ is infinite then for each $\epsilon > 0$ there exists an
integer $n$ such that $nA$ is $\epsilon$-dense and Berend-Peres later showed
that in fact one can take $n$ to be of the form $f(m)$ for any non-constant
$f(x) \in \mathbb{Z}[x]$. Alon and Peres provided a general framework for this
problem that has been used by Kelly-L\^{e} and Dong to show that the same
property holds for various linear actions on $\mathbb{T}^d$. We complement the
result of Kelly-L\^{e} on the $\epsilon$-dense images of integer polynomial
matrices in some subtorus of $\mathbb{T}^d$ by classifying those integer
polynomial matrices that have the Glasner property in the full torus
$\mathbb{T}^d$. We also extend a recent result of Dong by showing that if
$\Gamma \leq \operatorname{SL}_d(\mathbb{Z})$ is generated by finitely many
unipotents and acts irreducibly on $\mathbb{R}^d$ then the action $\Gamma
\curvearrowright \mathbb{T}^d$ has a uniform Glasner property. |
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| DOI: | 10.48550/arxiv.2103.08912 |