Condenser capacities and capacitary potentials for unbounded sets, and global $p$-harmonic Green functions on metric spaces

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Main Authors: Björn, Anders, Björn, Jana
Format: Preprint
Published: 2023
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author Björn, Anders
Björn, Jana
author_facet Björn, Anders
Björn, Jana
contents We study the condenser capacity $\mathrm{cap}_p(E,Ω)$ on \emph{unbounded} open sets $Ω$ in a proper connected metric space $X$ equipped with a locally doubling measure supporting a local $p$-Poincaré inequality, where $1<p<\infty$. Using a new definition of capacitary potentials, we show that $\mathrm{cap}_p$ is countably subadditive and that it is a Choquet capacity. We next obtain formulas for the capacity of superlevel sets for the capacitary potential. These are then used to show that $p$-harmonic Green functions exist in an unbounded domain $Ω$ if and only if either $X$ is $p$-hyperbolic or the Sobolev capacity $C_p(X\setminus Ω)>0$. As an application, we deduce new results for Perron solutions and boundary regularity for the Dirichlet boundary value problem for $p$-harmonic functions in unbounded open sets.
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id arxiv_https___arxiv_org_abs_2310_05702
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Condenser capacities and capacitary potentials for unbounded sets, and global $p$-harmonic Green functions on metric spaces
Björn, Anders
Björn, Jana
Analysis of PDEs
Functional Analysis
Primary: 31C45, Secondary: 30L99, 31C12, 31C15, 31E05, 35J08, 35J92, 46E36, 49Q20
We study the condenser capacity $\mathrm{cap}_p(E,Ω)$ on \emph{unbounded} open sets $Ω$ in a proper connected metric space $X$ equipped with a locally doubling measure supporting a local $p$-Poincaré inequality, where $1<p<\infty$. Using a new definition of capacitary potentials, we show that $\mathrm{cap}_p$ is countably subadditive and that it is a Choquet capacity. We next obtain formulas for the capacity of superlevel sets for the capacitary potential. These are then used to show that $p$-harmonic Green functions exist in an unbounded domain $Ω$ if and only if either $X$ is $p$-hyperbolic or the Sobolev capacity $C_p(X\setminus Ω)>0$. As an application, we deduce new results for Perron solutions and boundary regularity for the Dirichlet boundary value problem for $p$-harmonic functions in unbounded open sets.
title Condenser capacities and capacitary potentials for unbounded sets, and global $p$-harmonic Green functions on metric spaces
topic Analysis of PDEs
Functional Analysis
Primary: 31C45, Secondary: 30L99, 31C12, 31C15, 31E05, 35J08, 35J92, 46E36, 49Q20
url https://arxiv.org/abs/2310.05702