A counterexample regarding a two-phase problem for harmonic measure in VMO

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Main Author: Tolsa, Xavier
Format: Preprint
Published: 2024
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author Tolsa, Xavier
author_facet Tolsa, Xavier
contents Let $Ω^+\subset\mathbb R^{n+1}$ be a vanishing Reifenberg flat domain such that $Ω^+$ and $Ω^-=\mathbb R^{n+1}\setminus\overline {Ω^+}$ have joint big pieces of chord-arc subdomains and the outer unit normal to $Ω^+$ belongs to $VMO(ω^+)$, where $ω^\pm$ is the harmonic measure of $Ω^\pm$. Up to now it was an open question if these conditions imply that $\log\dfrac{dω^-}{dω^+} \in VMO(ω^+)$. In this paper we answer this question in the negative by constructing an appropriate counterexample in $\mathbb R^2$, with the additional property that the outer unit normal to $Ω^+$ is constant $ω^+$-a.e. in $\partialΩ^+$.
format Preprint
id arxiv_https___arxiv_org_abs_2401_14568
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A counterexample regarding a two-phase problem for harmonic measure in VMO
Tolsa, Xavier
Analysis of PDEs
Classical Analysis and ODEs
31B15, 31B20, 28A75
Let $Ω^+\subset\mathbb R^{n+1}$ be a vanishing Reifenberg flat domain such that $Ω^+$ and $Ω^-=\mathbb R^{n+1}\setminus\overline {Ω^+}$ have joint big pieces of chord-arc subdomains and the outer unit normal to $Ω^+$ belongs to $VMO(ω^+)$, where $ω^\pm$ is the harmonic measure of $Ω^\pm$. Up to now it was an open question if these conditions imply that $\log\dfrac{dω^-}{dω^+} \in VMO(ω^+)$. In this paper we answer this question in the negative by constructing an appropriate counterexample in $\mathbb R^2$, with the additional property that the outer unit normal to $Ω^+$ is constant $ω^+$-a.e. in $\partialΩ^+$.
title A counterexample regarding a two-phase problem for harmonic measure in VMO
topic Analysis of PDEs
Classical Analysis and ODEs
31B15, 31B20, 28A75
url https://arxiv.org/abs/2401.14568