Coercivity of combined boundary integral equations in high-frequency scattering

Euan A. Spence, Ilia V. Kamotski, Valery P. Smyshlyaev

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12 Citations (Scopus)
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Abstract

We prove that the standard second-kind integral equation formulation of the exterior Dirichlet problem for the Helmholtz equation is coercive (i.e., sign-definite) for all smooth convex domains when the wavenumber k is sufficiently large. (This integral equation involves the so-called combined potential, or combined field, operator.) This coercivity result yields k-explicit error estimates when the integral equation is solved using the Galerkin method, regardless of the particular approximation space used (and thus these error estimates apply to several hybrid numerical-asymptotic methods developed recently). Coercivity also gives k-explicit bounds on the number of GMRES iterations needed to achieve a prescribed accuracy when the integral equation is solved using the Galerkin method with standard piecewise-polynomial subspaces. The coercivity result is obtained by using identities for the Helmholtz equation originally introduced by Morawetz in her work on the local energy decay of solutions to the wave equation
Original languageEnglish
Pages (from-to)1587-1639
Number of pages53
JournalCommunications on Pure and Applied Mathematics
Volume68
Issue number9
Early online date6 Oct 2014
DOIs
Publication statusPublished - 1 Sep 2015

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