Contiguous relations, continued fractions and orthogonality

Gupta, Dharma; Masson, David

doi:10.1090/S0002-9947-98-01879-0

Contiguous relations, continued fractions and orthogonality
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by Dharma P. Gupta and David R. Masson PDF

Trans. Amer. Math. Soc. 350 (1998), 769-808 Request permission

Abstract:

We examine a special linear combination of balanced very-well-poised ${_{10} \phi _{9}}$ basic hypergeometric series that is known to satisfy a transformation. We call this $\Phi$ and show that it satisfies certain three-term contiguous relations. From two of these contiguous relations for $\Phi$ we obtain fifty-six pairwise linearly independent solutions to a three-term recurrence that generalizes the recurrence for Askey-Wilson polynomials. The associated continued fraction is evaluated using Pincherle’s theorem. From this continued fraction we are able to derive a discrete system of biorthogonal rational functions. This ties together Wilson’s results for rational biorthogonality, Watson’s $q$-analogue of Ramanujan’s Entry 40 continued fraction, and a conjecture of Askey concerning the latter. Some new $q$-series identities are also obtained. One is an important three-term transformation for $\Phi$’s which generalizes all the known two- and three-term ${_{8} \phi _{7}}$ transformations. Others are new and unexpected quadratic identities for these very-well-poised ${_{8} \phi _{7}}$’s.

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