Approximation of classes of periodic functions of several variables with given majorant of mixed moduli of continuity

Keywords:
mixed modulus of continuity, Bari-Stechkin condition, Nikol'skii-Besov-type class, linear operator, Vallée Poussin kernel, Fejér kernelAbstract
We obtain the exact-order estimates of approximation of the Nikol'skii-Besov-type classes BΩ∞,θBΩ∞,θ of periodic functions of several variables with a given function Ω(t)Ω(t) of a special form by using linear operators satisfying certain conditions. The approximation error is estimated in the metric of the space L∞L∞. The obtained estimates of the considered approximation characteristic, in addition to independent interest, can be used to establish the lower bounds of the orthowidths of the corresponding functional classes.