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On the Relation between the S-matrix and the Spectrum of the Interior Laplacian

A. G. Ramm (2009)

Bulletin of the Polish Academy of Sciences. Mathematics

The main results of this paper are: 1) a proof that a necessary condition for 1 to be an eigenvalue of the S-matrix is real analyticity of the boundary of the obstacle, 2) a short proof that if 1 is an eigenvalue of the S-matrix, then k² is an eigenvalue of the Laplacian of the interior problem, and that in this case there exists a solution to the interior Dirichlet problem for the Laplacian, which admits an analytic continuation to the whole space ℝ³ as an entire function.

On the relation of delay equations to first-order hyperbolic partial differential equations

Iasson Karafyllis, Miroslav Krstic (2014)

ESAIM: Control, Optimisation and Calculus of Variations

This paper establishes the equivalence between systems described by a single first-order hyperbolic partial differential equation and systems described by integral delay equations. System-theoretic results are provided for both classes of systems (among them converse Lyapunov results). The proposed framework can allow the study of discontinuous solutions for nonlinear systems described by a single first-order hyperbolic partial differential equation under the effect of measurable inputs acting on...

On the remainder in the Weyl formula for the Euclidean disk

Yves Colin de Verdière (2010/2011)

Séminaire de théorie spectrale et géométrie

We prove a 2-terms Weyl formula for the counting function N ( μ ) of the spectrum of the Laplace operator in the Euclidean disk with a sharp remainder estimate O μ 2 / 3 .

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