A Note on Approximation by Trigonometric Polynomials
- Authors: Shirokov N.A.1
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Affiliations:
- St. Petersburg State University and High School of Economics
- Issue: Vol 243, No 6 (2019)
- Pages: 981-984
- Section: Article
- URL: https://journals.rcsi.science/1072-3374/article/view/243195
- DOI: https://doi.org/10.1007/s10958-019-04598-y
- ID: 243195
Cite item
Abstract
Let \( E=\underset{k=1}{\overset{n}{\cup }}\left[{a}_k,{b}_k\right]\subset \mathbb{R} \); if n > 1, then we assume that the segments [ak, bk] are pairwise disjoint. Assume that the following property holds: E ∩ (E + 2πν) = ∅, ν ∈ ℤ, ν ≠ 0. Denote by Hω + r(E) the space of functions f defined on E such that |f(r)(x2) − f(r)(x1)| ≤ cfω(|x2 − x1|), x1, x2 ∈ E, f(0) ≡ f. Assume that a modulus of continuity ω satisfies the condition
We find a constructive description of the space Hω + r(E) in terms of the rate of nonuniform approximation of a function f ∈ Hω + r(E) by trigonometric polynomials if E and ω satisfy the above conditions.
About the authors
N. A. Shirokov
St. Petersburg State University and High School of Economics
Author for correspondence.
Email: nikolai.shirokov@gmail.com
Russian Federation, St. Petersburg