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arXiv · 2305.05535

Higher order boundary Harnack principles in Dini type domains

Seongmin Jeon·Stefano Vita
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Abstract

Aim of this paper is to provide higher order boundary Harnack principles [De Silva-Savin 15] for elliptic equations in divergence form under Dini type regularity assumptions on boundaries, coefficients and forcing terms. As it was proven in [Terracini-Tortone-Vita 22], the ratio $v/u$ of two solutions vanishing on a common portion $\Gamma$ of a regular boundary solves a degenerate elliptic equation whose coefficients behave as $u^2$ at $\Gamma$. Hence, for any $k\geq 1$ we provide $C^k$ estimates for solutions to the auxiliary degenerate equation under double Dini conditions, actually for general powers of the weight $a>-1$, and we imply $C^k$ estimates for the ratio $v/u$ under triple Dini conditions, as a corollary in the case $a=2$.

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Seongmin Jeon, Stefano Vita. 2023-05-09. Higher order boundary Harnack principles in Dini type domains. https://doi.org/10.1016/j.jde.2024.08.059

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