Dual generalized Bernstein basis

  • Authors:
  • Stanisław Lewanowicz;Paweł Woźny

  • Affiliations:
  • Institute of Computer Science, University of Wrocław, Wrocław, Poland;Institute of Computer Science, University of Wrocław, Wrocław, Poland

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

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Abstract

The generalized Bernstein basis in the space Πn of polynomials of degree at most n, being an extension of the q-Bernstein basis introduced by Philips [Bernstein polynomials based on the q-integers, Ann. Numer. Math. 4 (1997) 511-518], is given by the formula [S. Lewanowicz, P. Woźny, Generalized Bernstein polynomials, BIT Numer. Math. 44 (2004) 63-78] Bin(x; ω|q):= 1/(ωq)n[n, i]q xi(ωx-1;q)i(x; q)n-i (i=0,1,...,n). We give explicitly the dual basis functions Dkn(x; a, b, ω| q) for the polynomials Bin(x; ω| q), in terms of big q-Jacobi polynomials Pk (x; a, b, ω/q; q), a and b being parameters; the connection coefficients are evaluations of the q-Hahn polynomials. An inverse formula--relating big q-Jacobi, dual generalized Bernstein, and dual q-Hahn polynomials--is also given. Further, an alternative formula is given, representing the dual polynomial Djn (0 ≤ j ≤ n) as a linear combination of min(j, n - j) + 1 big q-Jacobi polynomials with shifted parameters and argument. Finally, we give a recurrence relation satisfied by Dkn, as well as an identity which may be seen as an analogue of the extended Marsden's identity [R.N. Goldman, Dual polynomial bases, J. Approx. Theory 79 (1994) 311-346].