Abstract:
Sharp estimates are derived for the convergence rate of Fourier series in terms of orthogonal systems of functions for certain classes of complex variable functions, and the Kolmogorov $N$-widths of these classes are determined. These issues find applications in numerical analysis methods.
Key words:orthogonal system of functions, completeness, Fourier series in terms of orthogonal systems, generalized modulus of continuity, Kolmogorov $N$-width, sharp estimates of convergence rate.