用三角多项式逼近连续周期函数的问题

Q4 Mathematics Researches in Mathematics Pub Date : 2021-10-06 DOI:10.15421/247711
V. Shalaev
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引用次数: 0

摘要

证明了$$1 - \frac{1}{2n} \leqslant \sup\limits_{\substack{f \in C\\f \ne const}} \frac{E_n(f)_C}{\omega_2(f; \pi/n)_C} \leqslant \inf\limits_{L_n \in Z_n(C)} \sup\limits_{\substack{f \in C\\f \ne const}} \frac{\| f - L_n(f) \|_C}{\omega_2 (f; \pi/n)_C} \leqslant 1$$其中$\omega_2(f; t)_C$是函数$f \in C$的光滑模,$E_n(f)_C$是一致度规中不大于$n-1$次的三角多项式的最佳逼近,$Z_n(C)$是将$C$映射到不大于$n-1$次的三角多项式的子空间的线性有界算子的集合。
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To the question of approximation of continuous periodic functions by trigonometric polynomials
In the paper, it is proved that$$1 - \frac{1}{2n} \leqslant \sup\limits_{\substack{f \in C\\f \ne const}} \frac{E_n(f)_C}{\omega_2(f; \pi/n)_C} \leqslant \inf\limits_{L_n \in Z_n(C)} \sup\limits_{\substack{f \in C\\f \ne const}} \frac{\| f - L_n(f) \|_C}{\omega_2 (f; \pi/n)_C} \leqslant 1$$where $\omega_2(f; t)_C$ is the modulus of smoothness of the function $f \in C$, $E_n(f)_C$ is the best approximation by trigonometric polynomials of the degree not greater than $n-1$ in uniform metric, $Z_n(C)$ is the set of linear bounded operators that map $C$ to the subspace of trigonometric polynomials of degree not greater than $n-1$.
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来源期刊
CiteScore
0.50
自引率
0.00%
发文量
8
审稿时长
16 weeks
期刊最新文献
On the analytic extension of three ratios of Horn's confluent hypergeometric function $\mathrm{H}_7$ Construction of a non-linear analytical model for the rotation parts building up process using regression analysis Automorphism groups of some non-nilpotent Leibniz algebras Some results on ultrametric 2-normed spaces Action of derivations on polynomials and on Jacobian derivations
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