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A commutant lifting theorem on analytic polyhedra

Calin Ambrozie, Jörg Eschmeier (2005)

Banach Center Publications

In this note a commutant lifting theorem for vector-valued functional Hilbert spaces over generalized analytic polyhedra in ℂⁿ is proved. Let T be the compression of the multiplication tuple M z to a *-invariant closed subspace of the underlying functional Hilbert space. Our main result characterizes those operators in the commutant of T which possess a lifting to a multiplier with Schur class symbol. As an application we obtain interpolation results of Nevanlinna-Pick and Carathéodory-Fejér type...

A conjecture on multivariate polynomial interpolation.

Jesús Miguel Carnicer, Mariano Gasca (2001)

RACSAM

La generalización de las fórmulas de interpolación de Lagrange y Newton a varias variables es uno de los temas habituales de estudio en interpolación polinómica. Dos clases de configuraciones geométricas particularmente interesantes en el plano fueron obtenidas por Chung y Yao en 1978 para la fórmula de Lagrange y por Gasca y Maeztu en 1982 para la de Newton. Estos últimos autores conjeturaron que toda configuración de la primera clase es de la segunda, y probaron que el recíproco no es cierto....

A Newton approach to bivariate Hermite interpolation on generalized natural lattices.

Jesús Miguel Carnicer, Mariano Gasca (2002)

RACSAM

Un retículo natural es el conjunto de todas las intersecciones de un conjunto de rectas del plano en posición general. El problema de interpolación de Lagrange sobre un retículo natural de n + 2 rectas tiene solución única en el espacio de los polinomios bivariados de grado menor o igual que n. Un retículo natural generalizado está formado por todas las intersecciones de un conjunto de rectas distintas, sin excluir paralelismos o concurrencias múltiples. A un retículo natural generalizado le asociamos...

A note on one of the Bernstein theorems

Jiří Brabec (1993)

Mathematica Bohemica

One of the Bernstein theorems that the class of bounded functions of the exponential type is dense in the space of bounded and uniformly continuous functions. This theorem follows from a convergence theorem for some interpolating operators on the real axis.

A note on the rate of convergence for Chebyshev-Lobatto and Radau systems

Elías Berriochoa, Alicia Cachafeiro, Jaime Díaz, Eduardo Martínez (2016)

Open Mathematics

This paper is devoted to Hermite interpolation with Chebyshev-Lobatto and Chebyshev-Radau nodal points. The aim of this piece of work is to establish the rate of convergence for some types of smooth functions. Although the rate of convergence is similar to that of Lagrange interpolation, taking into account the asymptotic constants that we obtain, the use of this method is justified and it is very suitable when we dispose of the appropriate information.

A particular smooth interpolation that generates splines

Segeth, Karel (2017)

Programs and Algorithms of Numerical Mathematics

There are two grounds the spline theory stems from – the algebraic one (where splines are understood as piecewise smooth functions satisfying some continuity conditions) and the variational one (where splines are obtained via minimization of some quadratic functionals with constraints). We use the general variational approach called 𝑠𝑚𝑜𝑜𝑡ℎ𝑖𝑛𝑡𝑒𝑟𝑝𝑜𝑙𝑎𝑡𝑖𝑜𝑛 introduced by Talmi and Gilat and show that it covers not only the cubic spline and its 2D and 3D analogues but also the well known tension spline (called also spline...

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