On the Bernstein-type inequalities for ultraspherical polynomials

  • Authors:
  • C. Giordano;A. Laforgia

  • Affiliations:
  • Dipartimento di Matematica, Università di Torino, Via Carlo Alberto 10, 10123 Torino, Italy;Dipartimento di Matematica, Università di Roma Tre, Largo S. Leonardo Murialdo, 1, Rome, Italy

  • Venue:
  • Journal of Computational and Applied Mathematics - Proceedings of the sixth international symposium on orthogonal polynomials, special functions and their applications
  • Year:
  • 2003

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Abstract

We present a survey of the most recent results and inequalities for the gamma function and the ratio of the gamma functions and study, among other things, the relation between these results and known inequalities for ultraspherical polynomials. In particular, we discuss the inequality (sin θ)λ|Pn(λ)(cos θ)| 1-λ/Γ(λ) Γ(n + 3/2λ)/Γ(n + 1 + 1/2λ), 0 ≤ θ ≤ π, where Pn(λ)(cos θ) denotes the ultraspherical polynomial of degree n, established by Alzer (Arch. Math. 69 (1997) 487) and the one established by Durand (In: R.A. Askey (Ed.), Theory and Application of Special Functions, Proceedings of the Advanced Seminar on Mathematical Research Center, University of Wisconsin, Madison, Vol. 35, Academic Press, New York, 1975, p. 353) (sin θ)λ|Pn(λ)(cos θ)| ≤ Γ(n/2 + λ)/Γ(λ)Γ(n/2 + 1), 0 ≤ θ ≤ π.