A uniqueness theorem for nonvariational solutions of the Helmholtz equation

Fuente: arXiv
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Main Author: de Cristoforis, M. Lanza
Format: Preprint
Published: 2025
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author de Cristoforis, M. Lanza
author_facet de Cristoforis, M. Lanza
contents We consider a bounded open subset $Ω$ of ${\mathbb{R}}^n$ of class $C^{1,α}$ for some $α\in]0,1[$, and we define a distributional outward unit normal derivative for $α$-Hölder continuous solutions of the Helmholtz equation in the exterior of $Ω$ that may not have a classical outward unit normal derivative at the boundary points of $Ω$ and that may have an infinite Dirichlet integral around the boundary of $Ω$. Namely for solutions that do not belong to the classical variational setting. Then we show a Schauder boundary regularity result for $α$-Hölder continuous functions that have the Laplace operator in a Schauder space of negative exponent and we prove a uniqueness theorem for $α$-Hölder continuous solutions of the exterior Dirichlet and impedance boundary value problems for the Helmholtz equation that satisfy the Sommerfeld radiation condition at infinity in the above mentioned nonvariational setting.
format Preprint
id arxiv_https___arxiv_org_abs_2504_11487
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A uniqueness theorem for nonvariational solutions of the Helmholtz equation
de Cristoforis, M. Lanza
Analysis of PDEs
31B10, 35J25, 35J05
We consider a bounded open subset $Ω$ of ${\mathbb{R}}^n$ of class $C^{1,α}$ for some $α\in]0,1[$, and we define a distributional outward unit normal derivative for $α$-Hölder continuous solutions of the Helmholtz equation in the exterior of $Ω$ that may not have a classical outward unit normal derivative at the boundary points of $Ω$ and that may have an infinite Dirichlet integral around the boundary of $Ω$. Namely for solutions that do not belong to the classical variational setting. Then we show a Schauder boundary regularity result for $α$-Hölder continuous functions that have the Laplace operator in a Schauder space of negative exponent and we prove a uniqueness theorem for $α$-Hölder continuous solutions of the exterior Dirichlet and impedance boundary value problems for the Helmholtz equation that satisfy the Sommerfeld radiation condition at infinity in the above mentioned nonvariational setting.
title A uniqueness theorem for nonvariational solutions of the Helmholtz equation
topic Analysis of PDEs
31B10, 35J25, 35J05
url https://arxiv.org/abs/2504.11487