An operator version of the Korovkin theorem

We prove the following operator version of the Korovkin theorem: Let T be a compact Hausdorff space, Vn:C[a,b]→C(T) a sequence of linear positive operators and A:C[a,b]→C(T) a linear positive operator such that A(1)A(e2)=[A(e1)]2 and A(1)(t)>0, ∀t∈T. If limn→∞⁡Vn(1)=A(1), limn→∞⁡Vn(e1)=A(e1), lim...

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Veröffentlicht in:Journal of mathematical analysis and applications 2022-11, Vol.515 (1), p.126375, Article 126375
1. Verfasser: Popa, Dumitru
Format: Artikel
Sprache:eng
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Zusammenfassung:We prove the following operator version of the Korovkin theorem: Let T be a compact Hausdorff space, Vn:C[a,b]→C(T) a sequence of linear positive operators and A:C[a,b]→C(T) a linear positive operator such that A(1)A(e2)=[A(e1)]2 and A(1)(t)>0, ∀t∈T. If limn→∞⁡Vn(1)=A(1), limn→∞⁡Vn(e1)=A(e1), limn→∞⁡Vn(e2)=A(e2) all uniformly on T, then for every f∈C[a,b], limn→∞⁡Vn(f)=A(f) uniformly on T. Many and various examples are given.
ISSN:0022-247X
1096-0813
DOI:10.1016/j.jmaa.2022.126375