Applying GMRES to the Helmholtz equation with shifted Laplacian preconditioning: what is the largest shift for which wavenumber-independent convergence is …

MJ Gander, IG Graham, EA Spence - Numerische Mathematik, 2015 - Springer
There has been much recent research on preconditioning discretisations of the Helmholtz
operator Δ+ k^ 2 Δ+ k 2 (subject to suitable boundary conditions) using a discrete version of …

The Burton and Miller method: Unlocking another mystery of its coupling parameter

S Marburg - Journal of Computational Acoustics, 2016 - World Scientific
The phenomenon of irregular frequencies or spurious modes when solving the Kirchhoff–
Helmholtz integral equation has been extensively studied over the last six or seven …

[HTML][HTML] The Helmholtz equation in heterogeneous media: a priori bounds, well-posedness, and resonances

IG Graham, OR Pembery, EA Spence - Journal of Differential Equations, 2019 - Elsevier
We consider the exterior Dirichlet problem for the heterogeneous Helmholtz equation, ie the
equation∇⋅(A∇ u)+ k 2 nu=− f where both A and n are functions of position. We prove new …

Acoustic transmission problems: wavenumber-explicit bounds and resonance-free regions

A Moiola, EA Spence - … Models and Methods in Applied Sciences, 2019 - World Scientific
We consider the Helmholtz transmission problem with one penetrable star-shaped Lipschitz
obstacle. Under a natural assumption about the ratio of the wavenumbers, we prove bounds …

Is the Helmholtz equation really sign-indefinite?

A Moiola, EA Spence - Siam Review, 2014 - SIAM
The usual variational (or weak) formulations of the Helmholtz equation are sign-indefinite in
the sense that the bilinear forms cannot be bounded below by a positive multiple of the …

Sharp high-frequency estimates for the Helmholtz equation and applications to boundary integral equations

D Baskin, EA Spence, J Wunsch - SIAM Journal on Mathematical Analysis, 2016 - SIAM
We consider three problems for the Helmholtz equation in interior and exterior domains in
R^d (d=2,3): the exterior Dirichlet-to-Neumann and Neumann-to-Dirichlet problems for …

Chapter 6: Overview of Variational Formulations for Linear Elliptic PDEs

EA Spence - Unified Transform for Boundary Value Problems …, 2014 - SIAM
6.1▪“When All Else Fails, Integrate by Parts”: New and Old Variational Formulations for
Linear Elliptic PDEs 6.1. 1▪ Introduction Although the motto “when all else fails, integrate by …

Wavenumber-explicit bounds in time-harmonic acoustic scattering

EA Spence - SIAM Journal on Mathematical Analysis, 2014 - SIAM
We prove wavenumber-explicit bounds on the Dirichlet-to-Neumann map for the Helmholtz
equation in the exterior of a bounded obstacle when one of the following three conditions …

High-frequency bounds for the Helmholtz equation under parabolic trapping and applications in numerical analysis

SN Chandler-Wilde, EA Spence, A Gibbs… - SIAM Journal on …, 2020 - SIAM
This paper is concerned with resolvent estimates on the real axis for the Helmholtz equation
posed in the exterior of a bounded obstacle with Dirichlet boundary conditions when the …

Wavenumber-explicit analysis for the Helmholtz h-BEM: error estimates and iteration counts for the Dirichlet problem

J Galkowski, EH Müller, EA Spence - Numerische Mathematik, 2019 - Springer
We consider solving the exterior Dirichlet problem for the Helmholtz equation with the h-
version of the boundary element method (BEM) using the standard second-kind combined …