The Parabolic Cylinder Function D v (x)

2008 ◽  
pp. 471-484
Author(s):  
Keith B. Oldham ◽  
Jan C. Myland ◽  
Jerome Spanier

A deeper understanding of the rich structure of the canonical form of the oscillatory integral describing the cusp diffraction catastrophe, generally known as Pearcey’s integral P '( X , Y ), can be obtained by considering its analytic continuation to arbitrary complex variables X and Y . A new integral representation for P '( X , Y ) is given in the form of a contour integral involving a Weber parabolic cylinder function whose order is the variable of integration. It is shown how the asymptotics of P '( X , Y ) may be obtained from this representation for complex X and Y when either | X | or | Y | → ∞, without reference to the usual stationary points of the integrand. For the case | X | → ∞, Y finite the full asymptotic expansion of P '( X , Y ) is derived and its asymptotic character is found to be either exponentially large or algebraic in certain sectors of the X - plane. The case | Y | → ∞ , X finite is complicated by the presence of exponentially small subdominant terms in certain sectors of the Y - plane, and only the first terms in the expansion are given. The asymptotic behaviour of P '( X , Y ) on the caustic Y 2 + (2/3 X ) 3 = 0 is also obtained from the new representation and is shown to agree with recent results of D. Kaminski. The various properties of the Weber parabolic cylinder function required in this paper are collected together in the Appendix.


Author(s):  
W. F. Kibble

It was shown by Mehler (1866) thatwhere Hk(x) denotes the Hermite polynomial(Hermite, 1864a, b), which can be expressed in terms of Weber's parabolic cylinder function (Whittaker, 1903). The series is convergent if | ρ | < 1, and divergent if | ρ | > 1. If ρ = 1 and x = y = 0 the series is divergent, and Hille's work (1938) shows that it will therefore be divergent for all real or complex values, except possibly real positive values, of x and y.


Sign in / Sign up

Export Citation Format

Share Document