Infinitely badly approximable affine forms

Fuente: arXiv
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Main Author: Kim, Taehyeong
Format: Preprint
Published: 2024
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author Kim, Taehyeong
author_facet Kim, Taehyeong
contents A pair $(A,\mathbf{b})$ of a real $m\times n$ matrix $A$ and $\mathbf{b}\in\mathbb{R}^m$ is said to be $\textit{infinitely badly approximable}$ if \[ \liminf_{\mathbf{q}\in\mathbb{Z}^n, \|\mathbf{q}\|\to\infty} \|\mathbf{q}\|^{\frac{n}{m}}\|A\mathbf{q}-\mathbf{b}\|_{\mathbb{Z}} =\infty, \] where $\|\cdot\|_\mathbb{Z}$ denotes the distance from the nearest integer vector. In this article, we introduce a novel concept of singularity for $(A,\mathbf{b})$ and characterize the infinitely badly approximable property by this singular property. As an application, we compute the Hausdorff dimension of the infinitely badly approximable set. We also discuss dynamical interpretations on the space of grids in $\mathbb{R}^{m+n}$.
format Preprint
id arxiv_https___arxiv_org_abs_2406_00821
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Infinitely badly approximable affine forms
Kim, Taehyeong
Number Theory
Dynamical Systems
A pair $(A,\mathbf{b})$ of a real $m\times n$ matrix $A$ and $\mathbf{b}\in\mathbb{R}^m$ is said to be $\textit{infinitely badly approximable}$ if \[ \liminf_{\mathbf{q}\in\mathbb{Z}^n, \|\mathbf{q}\|\to\infty} \|\mathbf{q}\|^{\frac{n}{m}}\|A\mathbf{q}-\mathbf{b}\|_{\mathbb{Z}} =\infty, \] where $\|\cdot\|_\mathbb{Z}$ denotes the distance from the nearest integer vector. In this article, we introduce a novel concept of singularity for $(A,\mathbf{b})$ and characterize the infinitely badly approximable property by this singular property. As an application, we compute the Hausdorff dimension of the infinitely badly approximable set. We also discuss dynamical interpretations on the space of grids in $\mathbb{R}^{m+n}$.
title Infinitely badly approximable affine forms
topic Number Theory
Dynamical Systems
url https://arxiv.org/abs/2406.00821