On the Lebesgue constant for the Xu interpolation formula

  • Authors:
  • Len Bos;Stefano De Marchi;Marco Vianello

  • Affiliations:
  • Department of Mathematics and Statistics, University of Calgary, Canada;Department of Computer Science, University of Verona, Verona, Italy;Department of Pure and Applied Mathematics, University of Padova, Italy

  • Venue:
  • Journal of Approximation Theory
  • Year:
  • 2006

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Abstract

In the paper [Y. Xu, Lagrange interpolation on Chebyshev points of two variables, J. Approx. Theory 87 (1996) 220-238], the author introduced a set of Chebyshev-like points for polynomial interpolation (by a certain subspace of polynomials) in the square [-1, 1]2, and derived a compact form of the corresponding Lagrange interpolation formula. In [L. Bos, M. Caliari, S. De Marchi, M. Vianello, A numerical study of the Xu polynomial interpolation formula in two variables, Computing 76(3-4) (2005) 311-324], we gave an efficient implementation of the Xu interpolation formula and we studied numerically its Lebesgue constant, giving evidence that it grows like O((log n)2), n being the degree. The aim of the present paper is to provide an analytic proof to show that the Lebesgue constant does have this order of growth.