Estimates of characteristics of nonlinear approximation of classes of periodic functions

Abstract

In the paper we make an overview of results concerning order estimates of the best m-term (sparse) trigonometric approximation and the best orthogonal trigonometric approximation of the Stepanets classes of multi- and univariate functions with bounded generalized derivatives in the Lebesque space. In addition, we formulate exact-order estimates for these approximation characteristics for the isotropic Nikol'skii-Besov classes with bounded differences in a certain Lebesque subspace. In particular, the case of small smoothness is considered of functions from the respective classes.