Abstract
We introduce and study a series of new moduli of smoothness in the multivariate case in \(L_p\)-spaces of periodic functions. The main focus lies on the case \(0<p<1\). We prove a direct Jackson-type estimate and provide necessary and sufficient conditions with respect to the dimension \(d\) and to integrability \(p\) for the equivalence of these moduli and polynomial \(K\)-functionals related to the Laplace-operator. As a consequence we obtain an inverse Bernstein-type estimate. Moreover, we are able to characterize the approximation error in case of approximation by families of linear polynomial operators which are generated by Bochner–Riesz kernels in terms of the introduced moduli.
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This research was supported by AvH-Foundation.
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Communicated by Paul Butzer.
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Runovski, K., Schmeisser, HJ. Moduli of Smoothness Related to the Laplace-Operator. J Fourier Anal Appl 21, 449–471 (2015). https://doi.org/10.1007/s00041-014-9373-y
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DOI: https://doi.org/10.1007/s00041-014-9373-y
Keywords
- Trigonometric approximation
- Fourier multipliers
- Moduli of smoothness
- \(K\)-functionals
- Jackson- and Bernstein-type theorems
- Bochner–Riesz means and families