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Approximation by harmonic polynomials in star-shaped domains and exponential convergence of Trefftz hp-dGFEM

Ralf Hiptmair, Andrea Moiola, Ilaria Perugia, Christoph Schwab (2014)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

We study the approximation of harmonic functions by means of harmonic polynomials in two-dimensional, bounded, star-shaped domains. Assuming that the functions possess analytic extensions to a δ-neighbourhood of the domain, we prove exponential convergence of the approximation error with respect to the degree of the approximating harmonic polynomial. All the constants appearing in the bounds are explicit and depend only on the shape-regularity of the domain and on δ. We apply the obtained estimates...

Approximation by p -Faber-Laurent rational functions in the weighted Lebesgue spaces

Daniyal M. Israfilov (2004)

Czechoslovak Mathematical Journal

Let L C be a regular Jordan curve. In this work, the approximation properties of the p -Faber-Laurent rational series expansions in the ω weighted Lebesgue spaces L p ( L , ω ) are studied. Under some restrictive conditions upon the weight functions the degree of this approximation by a k th integral modulus of continuity in L p ( L , ω ) spaces is estimated.

Approximations by the Cauchy-type integrals with piecewise linear densities

Jaroslav Drobek (2012)

Applications of Mathematics

The paper is a contribution to the complex variable boundary element method, shortly CVBEM. It is focused on Jordan regions having piecewise regular boundaries without cusps. Dini continuous densities whose modulus of continuity ω ( · ) satisfies lim sup s 0 ω ( s ) ln 1 s = 0 are considered on these boundaries. Functions satisfying the Hölder condition of order α , 0 < α 1 , belong to them. The statement that any Cauchy-type integral with such a density can be uniformly approximated by a Cauchy-type integral whose density is a piecewise...

Bérenger/Maxwell with Discontinous Absorptions : Existence, Perfection, and No Loss

Laurence Halpern, Jeffrey Rauch (2012/2013)

Séminaire Laurent Schwartz — EDP et applications

We analyse Bérenger’s split algorithm applied to the system version of the two dimensional wave equation with absorptions equal to Heaviside functions of x j , j = 1 , 2 . The methods form the core of the analysis [11] for three dimensional Maxwell equations with absorptions not necessarily piecewise constant. The split problem is well posed, has no loss of derivatives (for divergence free data in the case of Maxwell), and is perfectly matched.

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