Best mean-square approximation of functions defined on the real axis by entire functions of exponential type

Exact constants in Jackson-type inequalities are calculated in the space $L_2 (\mathbb{R})$ in the case where the quantity of the best approximation $\mathcal{A}_{\sigma}(f)$ is estimated from above by the averaged smoothness characteristic $\Phi_2(f, t) = \cfrac 1t \int^t_0||\Delta^2_h(f)||dh$. We...

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Datum:2012
Hauptverfasser: Vakarchuk, S. B., Вакарчук, С. Б.
Format: Artikel
Sprache:Russisch
Englisch
Veröffentlicht: Institute of Mathematics, NAS of Ukraine 2012
Online Zugang:https://umj.imath.kiev.ua/index.php/umj/article/view/2601
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Назва журналу:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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Zusammenfassung:Exact constants in Jackson-type inequalities are calculated in the space $L_2 (\mathbb{R})$ in the case where the quantity of the best approximation $\mathcal{A}_{\sigma}(f)$ is estimated from above by the averaged smoothness characteristic $\Phi_2(f, t) = \cfrac 1t \int^t_0||\Delta^2_h(f)||dh$. We also calculate the exact values of the average $\nu$-widths of classes of functions defined by $\Phi_2$.