Intermediate dimensions of infinitely generated attractors

Fuente: arXiv
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Autori principali: Banaji, Amlan, Fraser, Jonathan M.
Natura: Preprint
Pubblicazione: 2021
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author Banaji, Amlan
Fraser, Jonathan M.
author_facet Banaji, Amlan
Fraser, Jonathan M.
contents We study the dimension theory of limit sets of iterated function systems consisting of a countably infinite number of contractions. Our primary focus is on the intermediate dimensions: a family of dimensions depending on a parameter $θ\in [0,1]$ which interpolate between the Hausdorff and box dimensions. Our main results are in the case when all the contractions are conformal. Under a natural separation condition we prove that the intermediate dimensions of the limit set are the maximum of the Hausdorff dimension of the limit set and the intermediate dimensions of the set of fixed points of the contractions. This builds on work of Mauldin and Urbański concerning the Hausdorff and upper box dimension. We give several (often counter-intuitive) applications of our work to dimensions of projections, fractional Brownian images, and general Hölder images. These applications apply to well-studied examples such as sets of numbers which have real or complex continued fraction expansions with restricted entries. We also obtain several results without assuming conformality or any separation conditions. We prove general upper bounds for the Hausdorff, box and intermediate dimensions of infinitely generated attractors in terms of a topological pressure function. We also show that the limit set of a 'generic' infinite iterated function system has box and intermediate dimensions equal to the ambient spatial dimension, where 'generic' can mean either 'full measure' or 'comeagre.'
format Preprint
id arxiv_https___arxiv_org_abs_2104_15133
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle Intermediate dimensions of infinitely generated attractors
Banaji, Amlan
Fraser, Jonathan M.
Dynamical Systems
Classical Analysis and ODEs
Metric Geometry
28A80 (Primary), 37B10, 11K50 (Secondary)
We study the dimension theory of limit sets of iterated function systems consisting of a countably infinite number of contractions. Our primary focus is on the intermediate dimensions: a family of dimensions depending on a parameter $θ\in [0,1]$ which interpolate between the Hausdorff and box dimensions. Our main results are in the case when all the contractions are conformal. Under a natural separation condition we prove that the intermediate dimensions of the limit set are the maximum of the Hausdorff dimension of the limit set and the intermediate dimensions of the set of fixed points of the contractions. This builds on work of Mauldin and Urbański concerning the Hausdorff and upper box dimension. We give several (often counter-intuitive) applications of our work to dimensions of projections, fractional Brownian images, and general Hölder images. These applications apply to well-studied examples such as sets of numbers which have real or complex continued fraction expansions with restricted entries. We also obtain several results without assuming conformality or any separation conditions. We prove general upper bounds for the Hausdorff, box and intermediate dimensions of infinitely generated attractors in terms of a topological pressure function. We also show that the limit set of a 'generic' infinite iterated function system has box and intermediate dimensions equal to the ambient spatial dimension, where 'generic' can mean either 'full measure' or 'comeagre.'
title Intermediate dimensions of infinitely generated attractors
topic Dynamical Systems
Classical Analysis and ODEs
Metric Geometry
28A80 (Primary), 37B10, 11K50 (Secondary)
url https://arxiv.org/abs/2104.15133