Uniform asymptotic expansion for a class of polynomials biorthogonal on the unit circle |
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Authors: | N M Temme |
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Institution: | 1. Centre for Mathematics and Computer Science, P.O. Box 4079, 1009, AB Amsterdam, The Netherlands
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Abstract: | An asymptotic expansion including error bounds is given for polynomials {P n, Qn} that are biorthogonal on the unit circle with respect to the weight function (1?eiθ)α+β(1?e?iθ)α?β. The asymptotic parameter isn; the expansion is uniform with respect toz in compact subsets ofC{0}. The pointz=1 is an interesting point, where the asymptotic behavior of the polynomials strongly changes. The approximants in the expansions are confluent hyper-geometric functions. The polynomials are special cases of the Gauss hyper-geometric functions. In fact, with the results of the paper it follows how (in a uniform way) the confluent hypergeometric function is obtained as the limit of the hypergeometric function2 F 1(a, b; c; z/b), asb→±∞,z≠b, withz=0 as “transition” point in the uniform expansion. |
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