Approximation of Sobolev classes by polynomials and ridge functions

  • Authors:
  • V. N. Konovalov;D. Leviatan;V. E. Maiorov

  • Affiliations:
  • Institute of Mathematics, NAS of Ukraine, 01601 Kyiv, Ukraine;Raymond and Beverly Sackler School of Mathematical Sciences, Tel Aviv University, 69978 Tel Aviv, Israel;Technion I.I.T., 32000 Haifa, Israel

  • Venue:
  • Journal of Approximation Theory
  • Year:
  • 2009

Quantified Score

Hi-index 0.00

Visualization

Abstract

Let W"p^r(B^d) be the usual Sobolev class of functions on the unit ball B^d in R^d, and W"p^@?^,^r(B^d) be the subclass of all radial functions in W"p^r(B^d). We show that for the classes W"p^@?^,^r(B^d) and W"p^r(B^d), the orders of best approximation by polynomials in L"q(B^d) coincide. We also obtain exact orders of best approximation in L"2(B^d) of the classes W"p^@?^,^r(B^d) by ridge functions and, as an immediate consequence, we obtain the same orders in L"2(B^d) for the usual Sobolev classes W"p^r(B^d).