An inverse theorem of approximation theory of periodic functions in various metrics

1992 ◽  
Vol 52 (2) ◽  
pp. 791-798
Author(s):  
N. A. Il'yasov
2012 ◽  
Vol 62 (1) ◽  
Author(s):  
Ali Guven ◽  
Daniyal Israfilov

AbstractAn inverse theorem of the trigonometric approximation theory in Weighted Orlicz spaces is proved and the constructive characterization of the generalized Lipschitz classes defined in these spaces is obtained.


2021 ◽  
Vol 15 ◽  
pp. 60
Author(s):  
S.B. Vakarchuk ◽  
M.B. Vakarchuk

For classes of $2\pi$-periodic functions of two discrete variables, defined on grid set $\sigma_{q,p}$, we found exact values of Kolmogorov and linear quasiwidths of classes $W^{r,p}(l^2_{q,p})$ in $l^2_{q,p}$ space.


2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
Konstantin Runovski ◽  
Hans-Jürgen Schmeisser

Differential operators generated by homogeneous functionsψof an arbitrary real orders>0(ψ-derivatives) and related spaces ofs-smooth periodic functions ofdvariables are introduced and systematically studied. The obtained scale is compared with the scales of Besov and Triebel-Lizorkin spaces. Explicit representation formulas forψ-derivatives are obtained in terms of the Fourier transform of their generators. Some applications to approximation theory are discussed.


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