Inequalities for upper bounds of functionals on the classes $W^r H^{ω}$ and their applications

We show that the well-known results on estimates of upper bounds of functionals on the classes $W^r H^{ω}$ of periodic functions can be regarded as a special case of Kolmogorov-type inequalities for support functions of convex sets. This enables us to prove numerous new statements concerning the app...

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Bibliographic Details
Date:2000
Main Authors: Babenko, V. F., Korneichuk, N. P., Kofanov, V. A., Pichugov, S. A., Бабенко, В. Ф., Корнейчук, Н. П., Кофанов, В. А., Пичугов, С. А.
Format: Article
Language:Russian
English
Published: Institute of Mathematics, NAS of Ukraine 2000
Online Access:https://umj.imath.kiev.ua/index.php/umj/article/view/4398
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Journal Title:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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Summary:We show that the well-known results on estimates of upper bounds of functionals on the classes $W^r H^{ω}$ of periodic functions can be regarded as a special case of Kolmogorov-type inequalities for support functions of convex sets. This enables us to prove numerous new statements concerning the approximation of the classes $W^r H^{ω}$, establish the equivalence of these statements, and obtain new exact inequalities of the Bernstein-Nikol’skii type that estimate the value of the support function of the class $H^{ω}$ on the derivatives of trigonometric polynomials or polynomial splines in terms of the $L^{ϱ}$ -norms of these polynomials and splines.