arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.01985math.NAcs.NA
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最佳多项式逼近比勒让德投影收敛快多少?

How much faster does the best polynomial approximation converge than Legendre projection?

Haiyong Wang

摘要:

我们比较了最佳多项式逼近和Legendre及Chebyshev投影的收敛行为,并推导出解析函数和可微函数的Legendre投影在最大范数下的最佳收敛速度。对于解析函数,我们证明了次数$n$的最佳多项式逼近比相同次数的Legendre投影好$n^{1/2}$倍。然而,对于可微函数,如分段解析函数和函数的分数光滑,我们表明,最佳逼近是优于勒让德投影只有一些常数因子。我们的研究结果提供了一些新的见解勒让德投影的逼近能力。

英文摘要:

We compare the convergence behavior of best polynomial approximations and Legendre and Chebyshev projections and derive optimal rates of convergence of Legendre projections for analytic and differentiable functions in the maximum norm. For analytic functions, we show that the best polynomial approximation of degree $n$ is better than the Legendre projection of the same degree by a factor of $n^{1/2}$. For differentiable functions such as piecewise analytic functions and functions of fractional smoothness, however, we show that the best approximation is better than the Legendre projection by only some constant factors. Our results provide some new insights into the approximation power of Legendre projections.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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