On singular Galerkin discretizations for three models in high-frequency scattering

Fuente: arXiv
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Main Authors: Chaumont-Frelet, T., Sauter, S.
Format: Preprint
Published: 2026
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author Chaumont-Frelet, T.
Sauter, S.
author_facet Chaumont-Frelet, T.
Sauter, S.
contents We consider three common mathematical models for time-harmonic high frequency scattering: the Helmholtz equation in two and three spatial dimensions, a transverse magnetic problem in two dimensions, and Maxwell's equation in three dimensions with dissipative boundary conditions such that the continuous problem is well posed. In this paper, we construct meshes for popular (low order) Galerkin finite element discretizations such that the discrete system matrix becomes singular and the discrete problem is not well posed. This implies that a condition "the finite element space has to be sufficiently rich" in the form of a resolution condition - typically imposed for discrete well-posedness - is not an artifact from the proof by a compact perturbation argument but necessary for discrete stability of the Galerkin discretization.
format Preprint
id arxiv_https___arxiv_org_abs_2602_03428
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On singular Galerkin discretizations for three models in high-frequency scattering
Chaumont-Frelet, T.
Sauter, S.
Numerical Analysis
Analysis of PDEs
We consider three common mathematical models for time-harmonic high frequency scattering: the Helmholtz equation in two and three spatial dimensions, a transverse magnetic problem in two dimensions, and Maxwell's equation in three dimensions with dissipative boundary conditions such that the continuous problem is well posed. In this paper, we construct meshes for popular (low order) Galerkin finite element discretizations such that the discrete system matrix becomes singular and the discrete problem is not well posed. This implies that a condition "the finite element space has to be sufficiently rich" in the form of a resolution condition - typically imposed for discrete well-posedness - is not an artifact from the proof by a compact perturbation argument but necessary for discrete stability of the Galerkin discretization.
title On singular Galerkin discretizations for three models in high-frequency scattering
topic Numerical Analysis
Analysis of PDEs
url https://arxiv.org/abs/2602.03428