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Uniform asymptotic expansions for oblate spheroidal functions II: negative separation parameter λ

Published online by Cambridge University Press:  14 November 2011

T. M. Dunster
Affiliation:
Department of Mathematical Sciences, San Diego State University, San Diego, CA 92182-0314, U.S.A.

Abstract

In [3], uniform asymptotic expansions were derived for solutions of the oblate spheroidal wave equation (z2 − 1)d2p/dz2 + 2zdp/dz − (λ + μ2/(z2 − 1)) p = 0, for the case where the parameter μ is real and non-negative, the separation parameter λ is real and positive, and γ is purely imaginary (γ = iu). As u → ∞, uniform asymptotic expansions were derived involving elementary, Airy and Bessel functions, these being valid in certain subdomains of the complex z plane. In this paper the complementary case, where λ is real and negative, is considered. Asymptotic expansions are derived which are valid in certain subdomains of the half-plane |arg (z)| ≦ π/2, uniformly valid for u → ∞ with λ /u2 fixed and negative, and 0 ≦ μ/u ≦ − ½λ /u2 − δ, where δ is an arbitrary positive constant. Explicit error bounds are available for all the approximations.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1995

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References

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