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On greedy algorithm approximating Kolmogorov widths in Banach spaces. (English) Zbl 1310.41031

Summary: The greedy algorithm to produce \(n\)-dimensional subspaces \(X_n\) to approximate a compact set \(\mathcal{F}\) contained in a Hilbert space was introduced in the context of reduced basis method in [Y. Maday et al., J. Sci. Comput. 17, No. 1–4, 437–446 (2002; Zbl 1014.65115); C. R., Math., Acad. Sci. Paris 335, No. 3, 289–294 (2002; Zbl 1009.65066)]. The same algorithm works for a general Banach space and in this context was studied in [R. DeVore et al., Constr. Approx. 37, No. 3, 455–466 (2013; Zbl 1276.41021)]. In this paper we study the case \(\mathcal{F} \subset L_p\). If Kolmogorov diameters \(d_n(\mathcal{F})\) of \(\mathcal{F}\) decay as \(n^{- \alpha}\) we give an almost optimal estimate for the decay of \(\sigma_n : = \operatorname{dist}(\mathcal{F}, X_n)\). We also give some direct estimates of the form \(\sigma_n \leq C_n d_n(\mathcal{F})\).

MSC:

41A65 Abstract approximation theory (approximation in normed linear spaces and other abstract spaces)
46B06 Asymptotic theory of Banach spaces
Full Text: DOI

References:

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