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Error bounds for the Liouville–Green (or WKB) approximation

Published online by Cambridge University Press:  24 October 2008

F. W. J. Olver
Affiliation:
National Physical LaboratoryTeddingtonMiddlesex

Abstract

Error bounds are derived and examined for approximate solutions in terms of elementary functions of the differential equations

in which u is a positive parameter, the functions f and p are free from singularities and p does not vanish. Bounds are also obtained for the remainder terms in the asymptotic expansions of the solutions in descending powers of u. The variable x ranges over a real interval, finite or infinite or over a region of the complex plane, bounded or unbounded.

Applications are made to parabolic cylinder functions of large orders, and modified Bessel functions of large orders.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1961

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