Lower bounds for Kolmogorov widths in classes of convolutions with Neumann kernel
We obtain exact lower bounds for Kolmogorov $n$-widths in spaces $C$ and $L$ of classes of convolutions with Neumann kernel $N_{q,\beta}(t)=\sum\limits_{k=1}^{\infty}\dfrac{q^k}{k}\cos\left(kt-\dfrac{\beta\pi}{2}\right)$, ${q\in(0,1)}$, ${\beta\in\mathbb{R}}$, for all natural $n$ greater some number...
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| Date: | 2014 |
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| Keywords: | keywords |
| Main Authors: | , |
| Format: | Article |
| Language: | Ukrainian |
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Інститут математики НАН України
2014
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| Online Access: | https://trim.imath.kiev.ua/index.php/trim/article/view/15 |
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| Journal Title: | Transactions of Institute of Mathematics of NAS of Ukraine |
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Transactions of Institute of Mathematics of NAS of Ukraine| Summary: | We obtain exact lower bounds for Kolmogorov $n$-widths in spaces $C$ and $L$ of classes of convolutions with Neumann kernel $N_{q,\beta}(t)=\sum\limits_{k=1}^{\infty}\dfrac{q^k}{k}\cos\left(kt-\dfrac{\beta\pi}{2}\right)$, ${q\in(0,1)}$, ${\beta\in\mathbb{R}}$, for all natural $n$ greater some number which depends only on $q$. The obtained estimates coincided with the best uniform approximations by trigonometric polynomials of mentioned classes. It allows us obtain exact values for widths of these classes. |
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