Geodesic
$K$-Functionals and Exact Values of n-Widths of Certain Classes in the Spaces $C(2\pi )$ and $L_1(2\pi )$
Matematičeskie zametki, Tome 71 (2002) no. 4, pp. 522-531 
S. B. Vakarchuk. $K$-Functionals and Exact Values of n-Widths of Certain Classes in the Spaces $C(2\pi )$ and $L_1(2\pi )$. Matematičeskie zametki, Tome 71 (2002) no. 4, pp. 522-531. http://geodesic.mathdoc.fr/item/MZM_2002_71_4_a3/
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Voir la notice de l'article provenant de la source Math-Net.Ru

For classes of $2\pi$-periodic functions whose $K$-functionals are majorized by functions satisfying certain constraints, exact values of Kolmogorov, Bernstein, and trigonometric $n$-widths in the spaces $C(2\pi )$ and $L_1(2\pi )$ are obtained. Examples of majorants that satisfy the requirements stated in this paper are given.

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