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We consider the planar unit disk $\mathbb D$ as the reference configuration and a Jordan domain $\mathbb Y$ as the deformed configuration, and study the problem of extending a given boundary homeomorphism $\varphi \colon \partial \mathbb D…

Complex Variables · Mathematics 2020-08-25 Aleksis Koski , Jani Onninen

Given the planar unit disk as the source and a Jordan domain as the target, we study the problem of extending a given boundary homeomorphism as a Sobolev homeomorphism. For general targets, this Sobolev variant of the classical…

Complex Variables · Mathematics 2020-04-22 Pekka Koskela , Aleksis Koski , Jani Onninen

Let $\mathbb X$ and $\mathbb Y$ be $\ell$-connected Jordan domains, $\ell \in \mathbb N$, with rectifiable boundaries in the complex plane. We prove that any boundary homeomorphism $\varphi \colon \partial \mathbb X \to \partial \mathbb Y$…

Complex Variables · Mathematics 2018-12-06 Aleksis Koski , Jani Onninen

Let $\Omega \subset \mathbb{R}^n$ be a domain that supports the $p$-Poincar\'e inequality. Given a homeomorphism $\varphi \in L^1_p(\Omega)$, for $p>n$ we show the domain $\varphi(\Omega)$ has finite geodesic diameter. This result has a…

Functional Analysis · Mathematics 2013-09-10 Vladimir Gol'dshtein , Alexander Ukhlov

We consider conformal homeomorphisms $\varphi$ of generalized Jordan domains $U$ onto planar domains $\Omega$ %, possibly {\bf infinitely connected}, that satisfy both of the next two conditions: (1) at most countably many boundary…

Complex Variables · Mathematics 2023-02-09 Jun Luo , Xiao-Ting Yao

We give a full characterization of embeddings of the unit circle that admit a Sobolev homeomorphic extension to the unit disk. As a direct corollary, we establish that for quasiconvex target domains $\mathbb Y$, any homeomorphism $\varphi…

Complex Variables · Mathematics 2025-03-28 Aleksis Koski , Jani Onninen , Haiqing Xu

We extend the classical Carath\'eodory extension theorem to quasiconformal Jordan domains $( Y, d_{Y} )$. We say that a metric space $( Y, d_{Y} )$ is a quasiconformal Jordan domain if the completion $\overline{Y}$ of $( Y, d_{Y} )$ has…

Metric Geometry · Mathematics 2021-11-15 Toni Ikonen

Let $D$ and $\Omega$ be Jordan domains with Dini's smooth boundaries and and let $f:D\mapsto \Omega$ be a harmonic homeomorphism. The object of the paper is to prove the following result: If $f$ is quasiconformal, then $f$ is Lipschitz.…

Complex Variables · Mathematics 2014-07-08 David Kalaj

We show that Sobolev space $W^1_1(\Omega)$ of any planar one-connected domain $\Omega$ has the Bounded Approximation property. The result holds independently from the properties of the boundary of $\Omega$. The prove is based on a new…

Functional Analysis · Mathematics 2014-01-29 Maria Roginskaya , Michal Wojciechowski

Each homeomorphic parametrization of a Jordan curve via the unit circle extends to a homeomorphism of the entire plane. It is a natural question to ask if such a homeomorphism can be chosen so as to have some Sobolev regularity. This…

Complex Variables · Mathematics 2025-03-21 Ondrěj Bouchala , Jarmo Jääskeläinen , Pekka Koskela , Haiqing Xu , Xilin Zhou

Let $\Omega \subset \mathbb{R}^n$ be a bounded domain and $1 < p < \infty$. We characterize $(1,p)$-extension domains in terms of inequalities of Bourgain--Brezis--Mironescu type. More precisely, we show that $\Omega$ is a $(1,p)$-extension…

Functional Analysis · Mathematics 2026-04-28 Riddhi Mishra , Kaushik Mohanta

Let $\mathbb{X}$ be a Jordan domain satisfying hyperbolic growth conditions. Assume that $\varphi$ is a homeomorphism from the boundary $\partial \mathbb{X}$ of $\mathbb{X}$ onto the unit circle. Denote by $h$ the harmonic diffeomorphic…

Complex Variables · Mathematics 2021-04-19 Zhuang Wang , Haiqing Xu

We prove the following result. If $f$ is a harmonic quasiconformal mapping between two Jordan domains $D$ and $\Omega$ having $\mathscr{C}^1$ boundaries, then the function $f$ is globally H\"older continuous for every $\alpha<1$ but it is…

Complex Variables · Mathematics 2023-11-21 David Kalaj

We characterize bounded simply-connected planar $W^{1,p}$-extension domains for $1 < p <2$ as those bounded domains $\Omega \subset \mathbb R^2$ for which any two points $z_1,z_2 \in \mathbb R^2 \setminus \Omega$ can be connected with a…

Classical Analysis and ODEs · Mathematics 2024-10-10 Pekka Koskela , Tapio Rajala , Yi Ru-Ya Zhang

We show that a bounded planar simply connected domain $\Omega$ is a $W^{1,\,1}$-extension domain if and only if for every pair $x,y$ of points in $\Omega^c$ there exists a curve $\gamma \subset \Omega^c$ connecting $x$ and $y$ with $$…

Functional Analysis · Mathematics 2025-12-11 Pekka Koskela , Tapio Rajala , Yi Ru-Ya Zhang

We show that if an open arc J of the boundary of a Jordan domain $\Omega$ is rectifiable, then the derivative $\Phi$' of the Riemann map $\Phi: D\rightarrow \Omega$ from the open unit disk D onto $\Omega$ behaves as an $H^1$ function when…

Complex Variables · Mathematics 2018-08-01 V. Liontou , V. Nestoridis

We prove a monotone Sobolev extension theorem for maps to Jordan domains with rectifiable boundary in metric surfaces of locally finite Hausdorff 2-measure. This is then used to prove a uniformization result for compact metric surfaces by…

Metric Geometry · Mathematics 2026-01-16 Damaris Meier , Noa Vikman , Stefan Wenger

David maps are generalizations of classical planar quasiconformal maps for which the dilatation is allowed to tend to infinity in a controlled fashion. In this note we examine how these maps distort Hausdorff dimension. We show \vs…

Dynamical Systems · Mathematics 2007-05-23 S. Zakeri

We investigate non-homeomorphic mappings of Riemannian surfaces of Sobolev class. We have obtained some estimates of distortion of moduli of families of curves. We have proved that, under some conditions, these mappings have a continuous…

Complex Variables · Mathematics 2022-09-27 Evgeny Sevost'yanov , Oleksandr Dovhopiatyi , Nataliya Ilkevych , Vitalina Kalenska

The Riemann Mapping Theorem states existence of a conformal homeomorphism $\varphi$ of a simply connected plane domain $\Omega\subset\mathbb C$ with non-empty boundary onto the unit disc $\mathbb D\subset \mathbb C$. In the first part of…

Functional Analysis · Mathematics 2013-05-21 V. Gol'dshtein , A. Ukhlov
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