On the shielding effect of the Helmholtz equation

Research output: Contribution to journalArticle

Abstract

Hadamard-type instability has been known for over a century as a cause of illposedness of the Cauchy problem for elliptic PDEs. This ill-posedness manifests itself as evanescent modes growing exponentially when propagated in the reverse direction. Since every oscillating mode of the Laplace equation is evanescent, the ill-posedness of its Cauchy problem is solely due to Hadamard-type instability. The presence of the propagating modes and beams for the Helmholtz equation gives rise to an entirely different type of ill-posedness, hitherto unknown to the practice, and untreated by the theory, of inverse scattering. We will present this fundamental phenomenon of ill-posedness for the Helmholtz equation.

Original languageEnglish (US)
Pages (from-to)627-638
Number of pages12
JournalCommunications on Pure and Applied Mathematics
Volume61
Issue number5
DOIs
StatePublished - May 2008

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Helmholtz equation
Ill-posedness
Helmholtz Equation
Shielding
Laplace equation
Scattering
Cauchy Problem
Elliptic PDE
Inverse Scattering
Laplace's equation
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Unknown

ASJC Scopus subject areas

  • Mathematics(all)
  • Applied Mathematics

Cite this

On the shielding effect of the Helmholtz equation. / Chen, Yu.

In: Communications on Pure and Applied Mathematics, Vol. 61, No. 5, 05.2008, p. 627-638.

Research output: Contribution to journalArticle

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