Unique continuation principles for finite-element discretizations of the Laplacian

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Titel: Unique continuation principles for finite-element discretizations of the Laplacian
Autoren: Graham Cox, Scott MacLachlan, Luke Steeves
Quelle: Linear Algebra and its Applications. 727:84-111
Publication Status: Preprint
Verlagsinformationen: Elsevier BV, 2025.
Publikationsjahr: 2025
Schlagwörter: Mathematics - Spectral Theory, Mathematics - Analysis of PDEs, FOS: Mathematics, Mathematics - Numerical Analysis, Numerical Analysis (math.NA), Spectral Theory (math.SP), Analysis of PDEs (math.AP)
Beschreibung: Unique continuation principles are fundamental properties of elliptic partial differential equations, giving conditions that guarantee that the solution to an elliptic equation must be uniformly zero. Since finite-element discretizations are a natural tool to help gain understanding into elliptic equations, it is natural to ask if such principles also hold at the discrete level. In this work, we prove a version of the unique continuation principle for piecewise-linear and -bilinear finite-element discretizations of the Laplacian eigenvalue problem on polygonal domains in $\mathbb{R}^2$. Namely, we show that any solution to the discretized equation $-Δu = λu$ with vanishing Dirichlet and Neumann traces must be identically zero under certain geometric and topological assumptions on the resulting triangulation. We also provide a counterexample, showing that a nonzero \emph{inner solution} exists when the topological assumptions are not satisfied. Finally, we give an application to an eigenvalue interlacing problem, where the space of inner solutions makes an explicit appearance.
Publikationsart: Article
Sprache: English
ISSN: 0024-3795
DOI: 10.1016/j.laa.2025.07.029
DOI: 10.48550/arxiv.2410.08963
Zugangs-URL: http://arxiv.org/abs/2410.08963
Rights: CC BY
arXiv Non-Exclusive Distribution
Dokumentencode: edsair.doi.dedup.....5dfa180cbe3d0149e34c9ed6d7079199
Datenbank: OpenAIRE
Beschreibung
Abstract:Unique continuation principles are fundamental properties of elliptic partial differential equations, giving conditions that guarantee that the solution to an elliptic equation must be uniformly zero. Since finite-element discretizations are a natural tool to help gain understanding into elliptic equations, it is natural to ask if such principles also hold at the discrete level. In this work, we prove a version of the unique continuation principle for piecewise-linear and -bilinear finite-element discretizations of the Laplacian eigenvalue problem on polygonal domains in $\mathbb{R}^2$. Namely, we show that any solution to the discretized equation $-Δu = λu$ with vanishing Dirichlet and Neumann traces must be identically zero under certain geometric and topological assumptions on the resulting triangulation. We also provide a counterexample, showing that a nonzero \emph{inner solution} exists when the topological assumptions are not satisfied. Finally, we give an application to an eigenvalue interlacing problem, where the space of inner solutions makes an explicit appearance.
ISSN:00243795
DOI:10.1016/j.laa.2025.07.029