Abstract:
We obtain order-sharp estimates of best approximation for the classes $B^\Omega_{p,\theta}$ of periodic functions of several variables by trigonometric polynomials whose spectra are generated by the level surfaces of the function $\Omega(t)$.
Keywords:periodic function of several variables, trigonometric polynomial, level surface, Bari–Stechkin condition, Vallée-Poussin kernel, modulus of continuity, Hölder'd inequality.
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