English

Recurrence equations and their classical orthogonal polynomial solutions on a quadratic or q-quadratic lattice

Classical Analysis and ODEs 2019-01-14 v1

Abstract

Every classical orthogonal polynomial system pn(x)p_n(x) satisfies a three-term recurrence relation of the type pn+1(x)=(Anx+Bn)pn(x)Cnpn1(x) (n=0,1,2,,p10), p_{n+1}(x)=(A_nx+B_n)p_n(x)-C_np_{n-1}(x)~ (n=0,1,2,\ldots, p_{-1}\equiv 0), with CnAnAn1>0C_nA_nA_{n-1}>0. Moreover, Favard's theorem states that the converse is true. A general method to derive the coefficients AnA_n, BnB_n, CnC_n in terms of the polynomial coefficients of the divided-difference equations satisfied by orthogonal polynomials on a quadratic or qq-quadratic lattice is recalled. The Maple implementations rec2ortho of Koorwinder and Swarttouw or retode of Koepf and Schmersau were developed to identify classical orthogonal polynomials given by their three-term recurrence relation as special functions. The two implementations rec2ortho and retode do not handle classical orthogonal polynomials on a quadratic or qq-quadratic lattice. In this manuscript, the Maple implementation retode of Koepf and Schmersau is extended to cover classical orthogonal polynomials on quadratic or qq-quadratic lattices and to answer as application an open problem submitted by Alhaidari during the 14th International Symposium on Orthogonal Polynomials, Special Functions and Applications.

Keywords

Cite

@article{arxiv.1901.03672,
  title  = {Recurrence equations and their classical orthogonal polynomial solutions on a quadratic or q-quadratic lattice},
  author = {Daniel Duviol Tcheutia},
  journal= {arXiv preprint arXiv:1901.03672},
  year   = {2019}
}