English

Asymptotic estimates for the widths of classes of functions of high smoothness

Classical Analysis and ODEs 2023-04-11 v1

Abstract

We find two-sided estimates for Kolmogorov, Bernstein, linear and projection widths of the classes of convolutions of 2π2\pi-periodic functions φ\varphi, such that φ21\|\varphi\|_2\le1, with fixed generated kernels Ψβˉ\Psi_{\bar{\beta}}, which have Fourier series of the form k=1ψ(k)cos(ktβkπ/2),\sum\limits_{k=1}^\infty \psi(k)\cos(kt-\beta_k\pi/2), where ψ(k)0,\psi(k)\ge0, ψ2(k)<,βkR,\sum\psi^2(k)<\infty, \beta_k\in\mathbb{R}, in the space CC. It is shown that for rapidly decrising sequences ψ(k)\psi(k) (in particular, if limkψ(k+1)/ψ(k)=0\lim\limits_{k\rightarrow\infty}{\psi(k+1)}/{\psi(k)}=0) obtained estimates are asymptotic equalities. We establish that asymptotic equalities for widths of this classes are realized by trigonometric Fourier sums.

Keywords

Cite

@article{arxiv.2304.04586,
  title  = {Asymptotic estimates for the widths of classes of functions of high smoothness},
  author = {A. S. Serdyuk and I. V. Sokolenko},
  journal= {arXiv preprint arXiv:2304.04586},
  year   = {2023}
}

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14 pages