Приближение классов функций многих переменных их ортогональными проекциями на подпространства тригонометрических полиномов

Abstract

In the space Lq, 1<q<∞ we establish estimates for the orders of the best approximations of the classes of functions of many variablesB1,θ r and B p,α r by orthogonal projections of functions from these classes onto the subspaces of trigonometric polynomials. It is shown that, in many cases, the estimates obtained in the present work are better in order than in the case of approximation by polynomials with harmonics from the hyperbolic cross.