Dimensions of Furstenberg sets and an extension of Bourgain's projection theorem

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Hauptverfasser: Shmerkin, Pablo, Wang, Hong
Format: Preprint
Veröffentlicht: 2022
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author Shmerkin, Pablo
Wang, Hong
author_facet Shmerkin, Pablo
Wang, Hong
contents We show that the Hausdorff dimension of $(s,t)$-Furstenberg sets is at least $s+t/2+ε$, where $ε>0$ depends only on $s$ and $t$. This improves the previously best known bound for $2s<t\le 1+ε(s,t)$, in particular providing the first improvement since 1999 to the dimension of classical $s$-Furstenberg sets for $s<1/2$. We deduce this from a corresponding discretized incidence bound under minimal non-concentration assumptions, that simultaneously extends Bourgain's discretized projection and sum-product theorems. The proofs are based on a recent discretized incidence bound of T.~Orponen and the first author and a certain duality between $(s,t)$ and $(t/2,s+t/2)$-Furstenberg sets.
format Preprint
id arxiv_https___arxiv_org_abs_2211_13363
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Dimensions of Furstenberg sets and an extension of Bourgain's projection theorem
Shmerkin, Pablo
Wang, Hong
Classical Analysis and ODEs
Combinatorics
Metric Geometry
28A80 (Primary) 28A75, 28A78 (Secondary)
We show that the Hausdorff dimension of $(s,t)$-Furstenberg sets is at least $s+t/2+ε$, where $ε>0$ depends only on $s$ and $t$. This improves the previously best known bound for $2s<t\le 1+ε(s,t)$, in particular providing the first improvement since 1999 to the dimension of classical $s$-Furstenberg sets for $s<1/2$. We deduce this from a corresponding discretized incidence bound under minimal non-concentration assumptions, that simultaneously extends Bourgain's discretized projection and sum-product theorems. The proofs are based on a recent discretized incidence bound of T.~Orponen and the first author and a certain duality between $(s,t)$ and $(t/2,s+t/2)$-Furstenberg sets.
title Dimensions of Furstenberg sets and an extension of Bourgain's projection theorem
topic Classical Analysis and ODEs
Combinatorics
Metric Geometry
28A80 (Primary) 28A75, 28A78 (Secondary)
url https://arxiv.org/abs/2211.13363