On Some Estimate for the Norm of an Interpolation Projector

Let $Q_n=[0,1]^n$ be the unit cube in ${\mathbb R}^n$ and let $C(Q_n)$ be a space of continuous functions $f:Q_n\to{\mathbb R}$ with the norm $\|f\|_{C(Q_n)}:=\max_{x\in Q_n}|f(x)|.$ By $\Pi_1\left({\mathbb R}^n\right)$ denote a set of polynomials in $n$ variables of degree $\leq 1$, i. e., a set of...

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Main Author: Mikhail V. Nevskii
Format: Article
Language:English
Published: Yaroslavl State University 2022-06-01
Series:Моделирование и анализ информационных систем
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Online Access:https://www.mais-journal.ru/jour/article/view/1648
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author Mikhail V. Nevskii
author_facet Mikhail V. Nevskii
author_sort Mikhail V. Nevskii
collection DOAJ
description Let $Q_n=[0,1]^n$ be the unit cube in ${\mathbb R}^n$ and let $C(Q_n)$ be a space of continuous functions $f:Q_n\to{\mathbb R}$ with the norm $\|f\|_{C(Q_n)}:=\max_{x\in Q_n}|f(x)|.$ By $\Pi_1\left({\mathbb R}^n\right)$ denote a set of polynomials in $n$ variables of degree $\leq 1$, i. e., a set of linear functions on ${\mathbb R}^n$. The interpolation projector $P:C(Q_n)\to \Pi_1({\mathbb R}^n)$ with the nodes $x^{(j)}\in Q_n$ is defined by the equalities $Pf\left(x^{(j)}\right)= f\left(x^{(j)}\right)$, $j=1,$ $\ldots,$ $ n+1$. Let $\|P\|_{Q_n}$ be the norm of $P$ as an operator from $C(Q_n)$ to $C(Q_n)$. If $n+1$ is an Hadamard number, then there exists a non-degenerate regular simplex having the vertices at vertices of $Q_n$. We discuss some approaches to get inequalities of the form $||P||_{Q_n}\leq c\sqrt{n}$ for the norm of the corresponding projector $P$.
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spelling doaj-art-b1adcd9e5a4a433090cdc3155d5e768a2025-08-20T03:22:03ZengYaroslavl State UniversityМоделирование и анализ информационных систем1818-10152313-54172022-06-012929210310.18255/1818-1015-2022-2-92-1031266On Some Estimate for the Norm of an Interpolation ProjectorMikhail V. Nevskii0P. G. Demidov Yaroslavl State UniversityLet $Q_n=[0,1]^n$ be the unit cube in ${\mathbb R}^n$ and let $C(Q_n)$ be a space of continuous functions $f:Q_n\to{\mathbb R}$ with the norm $\|f\|_{C(Q_n)}:=\max_{x\in Q_n}|f(x)|.$ By $\Pi_1\left({\mathbb R}^n\right)$ denote a set of polynomials in $n$ variables of degree $\leq 1$, i. e., a set of linear functions on ${\mathbb R}^n$. The interpolation projector $P:C(Q_n)\to \Pi_1({\mathbb R}^n)$ with the nodes $x^{(j)}\in Q_n$ is defined by the equalities $Pf\left(x^{(j)}\right)= f\left(x^{(j)}\right)$, $j=1,$ $\ldots,$ $ n+1$. Let $\|P\|_{Q_n}$ be the norm of $P$ as an operator from $C(Q_n)$ to $C(Q_n)$. If $n+1$ is an Hadamard number, then there exists a non-degenerate regular simplex having the vertices at vertices of $Q_n$. We discuss some approaches to get inequalities of the form $||P||_{Q_n}\leq c\sqrt{n}$ for the norm of the corresponding projector $P$.https://www.mais-journal.ru/jour/article/view/1648hadamard matrixregular simplexlinear interpolationprojectornorm
spellingShingle Mikhail V. Nevskii
On Some Estimate for the Norm of an Interpolation Projector
Моделирование и анализ информационных систем
hadamard matrix
regular simplex
linear interpolation
projector
norm
title On Some Estimate for the Norm of an Interpolation Projector
title_full On Some Estimate for the Norm of an Interpolation Projector
title_fullStr On Some Estimate for the Norm of an Interpolation Projector
title_full_unstemmed On Some Estimate for the Norm of an Interpolation Projector
title_short On Some Estimate for the Norm of an Interpolation Projector
title_sort on some estimate for the norm of an interpolation projector
topic hadamard matrix
regular simplex
linear interpolation
projector
norm
url https://www.mais-journal.ru/jour/article/view/1648
work_keys_str_mv AT mikhailvnevskii onsomeestimateforthenormofaninterpolationprojector