Best approximation and moduli of smoothness: Computation and equivalence theorems

  • Authors:
  • Sergey Tikhonov

  • Affiliations:
  • Scuola Normale Superiore, Pisa Piazza dei Cavalieri 7, 56126 Italy

  • Venue:
  • Journal of Approximation Theory
  • Year:
  • 2008

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Abstract

In this paper we investigate the trigonometric series with the @b-general monotone coefficients. First, we study the uniform convergence criterion. The estimates of best approximations and moduli of smoothness of the series in uniform metrics are obtained in terms of coefficients. These results imply several important relations between moduli of smoothness of different orders (in particular, Marchaud-type inequality) and best approximations.