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JOURNALS // Matematicheskie Zametki // Archive

Mat. Zametki, 2016 Volume 99, Issue 6, Pages 904–920 (Mi mzm10189)

This article is cited in 2 papers

Asymptotic Equalities for Best Approximations for Classes of Infinitely Differentiable Functions Defined by the Modulus of Continuity

A. S. Serdyuk, I. V. Sokolenko

Institute of Mathematics, Ukrainian National Academy of Sciences

Abstract: We obtain asymptotic estimates for best approximations by trigonometric polynomials in the metric of the space $C(L_p)$ for classes of periodic functions expressible as convolutions of kernels $\Psi_\beta$ with Fourier coefficients decreasing to zero faster than any power sequence, and with functions $\varphi\in C$  $(\varphi\in L_p)$ whose moduli of continuity do not exceed the given majorant of $\omega(t)$. It is proved that, in the spaces $C$ and $L_1$, for convex moduli of continuity $\omega(t)$, the obtained estimates are asymptotically sharp.

Keywords: best approximation by trigonometric polynomials, periodic infinitely differentiable function, modulus of continuity, generalized Poisson kernel, linear approximation method, Kolmogorov–Nikol'skii problem.

UDC: 517.518.83

Received: 30.10.2012

DOI: 10.4213/mzm10189


 English version:
Mathematical Notes, 2016, 99:6, 901–915

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© Steklov Math. Inst. of RAS, 2024