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arXiv 2104.01229math.NAcs.NAmath.FA
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一致范数的抽样离散化

Sampling discretization of the uniform norm

Boris Kashin, Sergei Konyagin, Vladimir Temlyakov

摘要:

研究了在给定的有限维连续函数子空间上函数的一致范数的离散化问题。我们特别注意的情况下,三角多项式的频率从任意有限集与固定的基数。我们给出了两个不同的证明的事实,即对于任何$N$维的连续函数空间的子空间,它是足够的使用$e^{CN}$样本点的一个准确的上界的一致范数。以前的已知结果表明,一个不能改善的指数增长性的采样点的数量的一个好的离散化定理在一致的范数。此外,我们证明了一个一般性的结果,它连接上界的采样点的数量在离散定理的一致范数与最佳的$m$ -长期双线性逼近的Dirichlet核与给定的子空间。我们举例说明我们的技术的应用程序上的例子三角多项式。

英文摘要:

Discretization of the uniform norm of functions from a given finite dimensional subspace of continuous functions is studied. We pay special attention to the case of trigonometric polynomials with frequencies from an arbitrary finite set with fixed cardinality. We give two different proofs of the fact that for any $N$-dimensional subspace of the space of continuous functions it is sufficient to use $e^{CN}$ sample points for an accurate upper bound for the uniform norm. Previous known results show that one cannot improve on the exponential growth of the number of sampling points for a good discretization theorem in the uniform norm. Also, we prove a general result, which connects the upper bound on the number of sampling points in the discretization theorem for the uniform norm with the best $m$-term bilinear approximation of the Dirichlet kernel associated with the given subspace. We illustrate application of our technique on the example of trigonometric polynomials.

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