Pointwise estimates of coconvex approximation

• Autores: German A. Dzyubenko, D. Leviatan, I. A. Shevchuk
• Localización: Jaen journal on approximation, ISSN 1889-3066, ISSN-e 1989-7251, Vol. 6, Nº. 2, 2014, págs. 261-295
• Idioma: inglés
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• Resumen

  • Let f ∈ C (−1, 1) change its convexity in the interval. We are interested in estimating the degree of approximation of f by polynomials which are coconvex with it, namely, polynomials that change their convexity exactly at the points where f does. We obtain Nikolskii-type pointwise estimates for such constrained approximation.