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Operators approximating partial derivatives at vertices of triangulations by averaging

Josef Dalík (2010)

Mathematica Bohemica

Let 𝒯 h be a triangulation of a bounded polygonal domain Ω 2 , h the space of the functions from C ( Ω ¯ ) linear on the triangles from 𝒯 h and Π h the interpolation operator from C ( Ω ¯ ) to h . For a unit vector z and an inner vertex a of 𝒯 h , we describe the set of vectors of coefficients such that the related linear combinations of the constant derivatives Π h ( u ) / z on the triangles surrounding a are equal to u / z ( a ) for all polynomials u of the total degree less than or equal to two. Then we prove that, generally, the values of the...

Optimal cubature formulas in a reflexive Banach space

V. Vaskevich (2003)

Open Mathematics

Sequences of cubature formulas with a joint countable set of nodes are studied. Each cubature formula under consideration has only a finite number of nonzero weights. We call a sequence of such kind a multicubature formula. For a given reflexive Banach space it is shown that there is a unique optimal multicubature formula and the sequence of the norm of optimal error functionals is monotonically decreasing to 0 as the number of the formula nodes tends to infinity.

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