高平滑函数类宽度的渐近估计

IF 1 Q1 MATHEMATICS
A. Serdyuk, I. V. Sokolenko
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引用次数: 0

摘要

我们发现了Kolmogorov, Bernstein, $2\pi$ -周期函数$\varphi$的卷积类的线性和投影宽度的双边估计,例如$\|\varphi\|_2\le1$,具有固定生成的核$\Psi_{\bar{\beta}}$,其傅立叶级数的形式为$$\sum\limits_{k=1}^\infty \psi(k)\cos(kt-\beta_k\pi/2),$$,其中$\psi(k)\ge0,$$\sum\psi^2(k)<\infty, \beta_k\in\mathbb{R}$。结果表明,对于速降序列$\psi(k)$(特别是$\lim\limits_{k\rightarrow\infty}{\psi(k+1)}/{\psi(k)}=0$),得到的估计是渐近等式。我们建立了这类宽度的渐近等式是用三角傅里叶和来实现的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Asymptotic estimates for the widths of classes of functions of high smothness
We find two-sided estimates for Kolmogorov, Bernstein, linear and projection widths of the classes of convolutions of $2\pi$-periodic functions $\varphi$, such that $\|\varphi\|_2\le1$, with fixed generated kernels $\Psi_{\bar{\beta}}$, which have Fourier series of the form $$\sum\limits_{k=1}^\infty \psi(k)\cos(kt-\beta_k\pi/2),$$ where $\psi(k)\ge0,$ $\sum\psi^2(k)<\infty, \beta_k\in\mathbb{R}$. It is shown that for rapidly decreasing sequences $\psi(k)$ (in particular, if $\lim\limits_{k\rightarrow\infty}{\psi(k+1)}/{\psi(k)}=0$) the obtained estimates are asymptotic equalities. We establish that asymptotic equalities for widths of this classes are realized by trigonometric Fourier sums.
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来源期刊
CiteScore
1.90
自引率
12.50%
发文量
31
审稿时长
25 weeks
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