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Zapiski Nauchnykh Seminarov POMI, 2021, Volume 499, Pages 22–37
(Mi znsl7059)
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I
Non-saturated estimates of the Kotelnikov formula error
O. L. Vinogradov Saint Petersburg State University
Abstract:
We estimate the error of approximation by Kotelnikov sums
$$U_Tf(x)= \sum_{j\in\Bbb Z}f\left(\frac{j}{T}\right)\mathrm{sinc}(Tx-j),\quad T>0,\quad \mathrm{sinc}{z}=\frac{\sin{\pi z}}{\pi z}.$$
Let $f\in\mathbf{A}$, i.e. $f(x)=\int_{\Bbb R}g(y)e^{ixy}\,dy$, $g\in L_1(\Bbb R)$, and let $\|f\|_\mathbf{A}=\int_{\Bbb R}|g|$ iz Wiener norm of $f$. Then the sharp inequality
$$\|f-U_Tf\|_{\mathbf A}\leqslant 2A_{T\pi}(f)_{\mathbf A}$$ holds, where $A_{\sigma}(f)_{\mathbf{A}}$ is the best approximation of $f$ in the Wiener norm by entire functions of type not exceeding $\sigma$. We also establish non-saturated uniform estimates.
Key words and phrases:
Kotelnikov formula, best approximation, Wiener algebra.
Received: 10.11.2020
Citation:
O. L. Vinogradov, “Non-saturated estimates of the Kotelnikov formula error”, Investigations on applied mathematics and informatics. Part I, Zap. Nauchn. Sem. POMI, 499, POMI, St. Petersburg, 2021, 22–37
Linking options:
https://www.mathnet.ru/eng/znsl7059 https://www.mathnet.ru/eng/znsl/v499/p22
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Abstract page: | 127 | Full-text PDF : | 37 | References: | 18 |
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