Hostname: page-component-cd9895bd7-jn8rn Total loading time: 0 Render date: 2024-12-28T13:38:46.697Z Has data issue: false hasContentIssue false

An infinite Legendre integral transform and its inverse

Published online by Cambridge University Press:  24 October 2008

P. C. Clemmow
Affiliation:
Cavendish LaboratoryCambridge

Abstract

A consideration of Legendre's equation, of order zero, expressed in terms of the angular variable θ, leads heuristically, but methodically, to an infinite integral representation of the delta function in terms of two independent non-periodic solutions Ev−½(θ), Ev−½(θ). This result yields an integral transform and inverse formula, where in the former the kernel is Ev−½(θ) sin θ and the integration over θ runs from − ∞ to ∞. By rigorous contour integral methods, the inverse is verified when the original function is a rectangular pulse, and the standard series expansion in terms of Legendre polynomials is recovered when the original function is even and of period 2π in θ. Analogies with the theory of Fourier transforms are emphasized.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1961

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

(1)Erdélyi, A. (Editor). Higher transcendental functions, vol. 1 (New York, 1953).Google Scholar
(2)Felsen, L. B.Trans. I.B.E. AP—7 (1959), 169.CrossRefGoogle Scholar
(3)Friedman, B.Principles and techniques of applied mathematics (London, 1956).Google Scholar
(4)Hobson, E. W.The theory of spherical and ellipsoidal harmonics (Cambridge, 1931).Google Scholar
(5)Marcuvitz, N.Comm. Pure Appl. Math. 4 (1951), 263.CrossRefGoogle Scholar
(6)Snow, C.Hypergeometric and Legendre functions with applications to integral equations of potential theory, National Bureau of Standards. Applied Mathematics series 19 (Washington, 1952).Google Scholar
(7)Titchmarsh, E. C.Eigenfunction expansions associated with second-order differential equations (Oxford, 1946).Google Scholar