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We give a concrete sufficient condition for a simply-connected domain to be the image of the unit disk under a nonexpansive conformal map. This class of domains is also characterized by having sufficiently dense harmonic measure. The…

Complex Variables · Mathematics 2018-07-10 Leonid V. Kovalev

We show that if $n\geq 1$, $\Omega\subset \mathbb R^{n+1}$ is a connected domain with porous boundary, and $E\subset \partial\Omega$ is a set of finite and positive Hausdorff $H^{n}$-measure upon which the harmonic measure $\omega$ is…

Classical Analysis and ODEs · Mathematics 2015-06-01 Jonas Azzam , Mihalis Mourgoglou , Xavier Tolsa

We study boundary regularity for conformally compact Einstein metrics in even dimensions by generalizing the ideas of Michael Anderson. Our method of approach is to view the vanishing of the Ambient Obstruction tensor as an nth order system…

Differential Geometry · Mathematics 2008-04-08 Dylan Helliwell

It was recently shown that the harmonic measure is absolutely continuous with respect to the Hausdorff measure on a domain with an $n-1$ dimensional uniformly rectifiable boundary, in the presence of now well understood additional…

Analysis of PDEs · Mathematics 2020-06-29 G. David , S. Mayboroda

It is a longstanding conjecture that given a subset $E$ of a metric space, if $E$ has finite Hausdorff measure in dimension $\alpha\ge 0$ and $\mathscr{H}^\alpha\llcorner E$ has unit density almost everywhere, then $E$ is an…

Metric Geometry · Mathematics 2022-07-01 Antoine Julia , Andrea Merlo

We consider a generalized Cantor set $E(\omega)$ for an infinite sequence $\omega=(q_n)_{n=1}^{\infty}\in (0, 1)^{\mathbb N}$, and consider the moduli space $M(\omega)$ for $\omega$ which are the set of $\omega'$ for which $E(\omega')$ is…

Complex Variables · Mathematics 2024-04-03 Hiroshige Shiga

In this paper, we obtain \textit{quantitative} estimates on the fine structure of the singular set of the mutual boundary $\partial \Omega^{\pm}$ for pairs of complementary domains, $\Omega^+, \Omega^- \subset \mathbb{R}^n$ which arise in a…

Analysis of PDEs · Mathematics 2024-05-22 Sean McCurdy

In a two dimensional annulus $A_\rho=\{x\in \mathbb R^2: \rho<|x|<1\}$, $\rho\in (0,1)$, we characterize $0$-homogeneous minimizers, in $H^1(A_\rho;\mathbb S^1)$ with respect to their own boundary conditions, of the anisotropic energy…

Analysis of PDEs · Mathematics 2024-09-10 Andres Contreras , Xavier Lamy

We compare the regularity of the boundary of a convex set with the value of its Finslerian volume entropy. The main result states that the volume entropy of a two-dimensional domain whose associated curvature measure is Ahlfors…

Metric Geometry · Mathematics 2020-01-10 Jan Cristina , Louis Merlin

In this paper we consider the specification property for $(\alpha,\beta)$-shifts. When $\alpha=0$, Schmeling shows that the set of $\beta>1$ for which the $\beta$-shift has the specification property has the Lebesgue measure zero but has…

Dynamical Systems · Mathematics 2024-03-22 Mai Oguchi , Mao Shinoda

For all $1<p<\infty$ and $N\ge 2$ we prove that there is a constant $\alpha(p,N)>0$ such that the $p$-harmonic measure in $\R^N_+$ of a ball of radius $0 < \delta \leq 1$ in $\R^{N-1}$ is bounded above and below by a constant times $\delta…

Analysis of PDEs · Mathematics 2018-07-30 J. G. Llorente , J. J. Manfredi , W. C. Troy , J. M. Wu

In this paper, we are concerned with the precise relationship between the Hausdorff dimension of possible singular point set $\mathcal{S}$ of suitable weak solutions and the parameter $\alpha$ in the nonlinear term in the following…

Analysis of PDEs · Mathematics 2022-05-02 Yanqing Wang , Yike Huang , Gang Wu , Daoguo Zhou

In the present paper we sketch the proof of the fact that for any open connected set $\Omega\subset\mathbb{R}^{n+1}$, $n\geq 1$, and any $E\subset \partial \Omega$ with $0<\mathcal{H}^n(E)<\infty$, absolute continuity of the harmonic…

Classical Analysis and ODEs · Mathematics 2018-10-10 Jonas Azzam , Steve Hofmann , José María Martell , Svitlana Mayboroda , Mihalis Mourgoglou , Xavier Tolsa , Alexander Volberg

We consider (not self-similar) Cantor sets defined by a sequence of piecewise linear functions. We prove that the dimension of the harmonic measure on such a set is strictly smaller than its Hausdorff dimension. Some Hausdorff measure…

Classical Analysis and ODEs · Mathematics 2013-03-19 Athanasios Batakis , Anna Zdunik

It is well-known that quantitative, scale invariant absolute continuity (more precisely, the weak-$A_\infty$ property) of harmonic measure with respect to surface measure, on the boundary of an open set $ \Omega\subset \mathbb{R}^{n+1}$…

Classical Analysis and ODEs · Mathematics 2020-08-13 Jonas Azzam , Steve Hofmann , José María Martell , Mihalis Mourgoglou , Xavier Tolsa

We examine caloric measures $\omega$ on general domains in $\mathbb{R}^{n+1} = \mathbb{R}^n\times\mathbb{R}$ (space $\times$ time) from the perspective of geometric measure theory. On one hand, we give a direct proof of a consequence of a…

Classical Analysis and ODEs · Mathematics 2023-07-13 Matthew Badger , Alyssa Genschaw

In this work, we revisit the following estimate due to Dahlberg \cite{Dahl}. Let $\textit{\textbf x}_0$ a fixed point in a bounded Lipschitz domain $\Omega$. Then there exists a constant $C > 0$ such that if $u$ is a harmonic function in…

Analysis of PDEs · Mathematics 2026-01-12 Chérif Amrouche , Mohand Moussaoui

This paper extends some results of [M5] and [M3], in particular, removing assumptions of positive lower density. We give conditions on a general family $P_{\lambda}:\mathbb{R}^{n}\to\mathbb{R}^{m}, \lambda \in \Lambda,$ of orthogonal…

Classical Analysis and ODEs · Mathematics 2023-10-12 Pertti Mattila

Considerable attention has been given to the study of the arithmetic sum of two planar sets. We focus on understanding the measure and dimension of $A+\Gamma:=\left\{a+v:a\in A, v\in \Gamma \right\}$ when $A\subset \mathbb{R}^2$ and…

Classical Analysis and ODEs · Mathematics 2022-08-15 Károly Simon , Krystal Taylor

We study the invariant measure of a discretized stochastic Allen-Cahn equation in d+1 dimensions in the low noise limit. We consider a cuboidal domain and impose the two stable phases as boundary conditions at two opposite faces. We then…

Probability · Mathematics 2010-12-14 Matthias Erbar