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Uniform Lebesgue constants of local spline approximation
V. T. Shevaldin Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg
Abstract:
Let a function $\varphi\in C^1[-h,h]$ be such that $\varphi(0)=\varphi'(0)=0$, $\varphi(-x)=\varphi(x)$ for $x\in [0;h])$, and $\varphi(x)$ is nondecreasing on $[0;h]$. For any function $f:\ \mathbb R\to \mathbb R$, we consider local splines of the form $$S(x)=S_{\varphi}(f,x)=\sum_{j\in \mathbb Z} y_j B_{\varphi}\Big( x+\frac{3h}{2}-jh\Big)\quad (x\in \mathbb R),$$ where $y_j=f(jh)$, $m(h)>0$, and $$B_{\varphi}(x)=m(h)\left\{ \begin{array}{cl}\varphi(x),& x\in [0;h],\\ 2\varphi(h)-\varphi(x-h)-\varphi(2h-x),& x\in [h;2h], \\ \varphi(3h-x),& x\in [2h;3h],\\ 0, & x\not\in [0;3h]. \end{array} \right.$$ These splines become parabolic, exponential, trigonometric, etc., under the corresponding choice of the function $\varphi$. We study the uniform Lebesgue constants $L_{\varphi}=\|S\|_C^C$ (the norms of linear operators from $C$ to $C$) of these splines as functions depending on $\varphi$ and $h$. In some cases, the constants are calculated exactly on the axis $\mathbb R$ and on a closed interval of the real line (under a certain choice of boundary conditions from the spline $S_{\varphi}(f,x)$).
Keywords:
Lebesgue constants, local splines, three-point system.
Received: 02.06.2017
Citation:
V. T. Shevaldin, “Uniform Lebesgue constants of local spline approximation”, Trudy Inst. Mat. i Mekh. UrO RAN, 23, no. 3, 2017, 292–299; Proc. Steklov Inst. Math. (Suppl.), 303, suppl. 1 (2018), 196–202
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https://www.mathnet.ru/eng/timm1459 https://www.mathnet.ru/eng/timm/v23/i3/p292
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Abstract page: | 203 | Full-text PDF : | 45 | References: | 38 | First page: | 12 |
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