Powered by OpenAIRE graph
Found an issue? Give us feedback
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ Studia Mathematicaarrow_drop_down
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
Studia Mathematica
Article
Data sources: UnpayWall
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
zbMATH Open
Article
Data sources: zbMATH Open
Studia Mathematica
Article . 2003 . Peer-reviewed
Data sources: Crossref
versions View all 2 versions
addClaim

Some theorems of Korovkin type

Authors: Hachiro, Tomoko; Okayasu, Takateru;

Some theorems of Korovkin type

Abstract

Summary: We take another approach to the well known theorem of Korovkin, in the following situation: \(X\),~\(Y\) are compact Hausdorff spaces, \(M\)~is a unital subspace of the Banach space \(C(X)\) (respectively, \(C_{{\mathbb R}}(X)\)) of all complex-valued (resp., real-valued) continuous functions on~\(X\), \(S\subset M\) a complex (resp., real) function space on~\(X\), \(\{\phi_{n}\}\)~a~sequence of unital linear contractions from \(M\) into~\(C(Y)\) (resp., \(C_{{\mathbb R}}(Y)\)), and \(\phi_{\infty}\) a linear isometry from \(M\) into~\(C(Y)\) (resp., \(C_{{\mathbb R}}(Y)\)). We show, under the assumption that \({\varPi}_{N} \subset {\varPi}_{T}\), where \({\varPi}_{N}\) is the Choquet boundary for \(N = \text{Span} (\bigcup_{1\leq n\leq \infty}N_n)\), \(N_n=\phi_{n}(M)\) (\(n=1,2,\ldots,\infty\)), and \({\varPi}_{T}\) the Choquet boundary for \(T=\phi_{\infty}(S)\), that \(\{\phi_{n}(f)\}\) converges pointwise to \(\phi_{\infty}(f)\) for any \(f\in M\) provided \(\{\phi_{n}(f)\}\) converges pointwise to \(\phi_{\infty}(f)\) for any \(f\in S\); that \(\{\phi_{n}(f)\}\) converges uniformly on any compact subset of~\({\varPi}_N\) to \(\phi_{\infty}(f)\) for any \(f\in M\) provided \(\{\phi_{n}(f)\}\) converges uniformly to \(\phi_{\infty}(f)\) for any \(f\in S\); and that, in the case where \(S\) is a function algebra, the \(\{\phi_n\}\) norm converges to~\(\phi_{\infty}\) on~\(M\) provided the \(\{\phi_{n}(f)\}\) norm converges to~\(\phi_{\infty}\) on~\(S\). The proofs are in the spirit of the original one for the theorem of Korovkin.

Related Organizations
Keywords

function space, linear contraction, Banach spaces of continuous, differentiable or analytic functions, Approximation by positive operators, Korovkin type approximation

  • BIP!
    Impact byBIP!
    selected citations
    These citations are derived from selected sources.
    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    1
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    Average
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Average
Powered by OpenAIRE graph
Found an issue? Give us feedback
selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
1
Average
Average
Average
bronze