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Integral Equations VIA Saddle Point Problem for 2D Electromagnetic Problems

Nathalie Bartoli, Francis Collino (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

A new system of integral equations for the exterior 2D time harmonic scattering problem is investigated. This system was first proposed by B. Després in [11]. Two new derivations of this system are given: one from elementary manipulations of classical equations, the other based on a minimization of a quadratic functional. Numerical issues are addressed to investigate the potential of the method.

Integral operators generated by Mercer-like kernels on topological spaces

M. H. Castro, V. A. Menegatto, A. P. Peron (2012)

Colloquium Mathematicae

We analyze some aspects of Mercer's theory when the integral operators act on L²(X,σ), where X is a first countable topological space and σ is a non-degenerate measure. We obtain results akin to the well-known Mercer's theorem and, under a positive definiteness assumption on the generating kernel of the operator, we also deduce series representations for the kernel, traceability of the operator and an integration formula to compute the trace. In this way, we upgrade considerably similar results...

Integral representations of unbounded operators by infinitely smooth kernels

Igor Novitskiî (2005)

Open Mathematics

In this paper, we prove that every unbounded linear operator satisfying the Korotkov-Weidmann characterization is unitarily equivalent to an integral operator in L 2(R), with a bounded and infinitely smooth Carleman kernel. The established unitary equivalence is implemented by explicitly definable unitary operators.

Integro-differential equations with time-varying delay

Chocholatý, Pavol (2013)

Programs and Algorithms of Numerical Mathematics

Integro-differential equations with time-varying delay can provide us with realistic models of many real world phenomena. Delayed Lotka-Volterra predator-prey systems arise in ecology. We investigate the numerical solution of a system of two integro-differential equations with time-varying delay and the given initial function. We will present an approach based on q -step methods using quadrature formulas.

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