In this paper, we compute upper bounds for the best approximation by trigonometric polynomials in the metrics and on the classes of 2-periodic functions such that , where is a given convex modulus of… Expand

Exact values of linear widths (diameters), Kolmogorov widths and Gel'fand widths, in -spaces are found for some classes of functions, using a convex majorant of the modulus of continuity of a… Expand

In this article we obtain characteristic properties of piecewise-polynomial functions (spline functions) that have least deviation from zero in the metric of C. This has allowed us to obtain… Expand

New results are obtained in this paper which elucidate properties of differentiable periodic functions connected with rearrangements. These results are applied in order to obtain a sharp estimate of… Expand