© 1997 by Oxford University Press
UNIFORM BOUNDS FOR Pnm(cos
) AND THE ABSOLUTE CONVERGENCE OF SERIES EXPANSIONS IN SPHERICAL SURFACE HARMONICS
( Department of Mathematics, University of Manchester Oxford Road, Manchester M13 9PL )
An arbitrary function f(
,
) (where r,
,
are a set of spherical polar co-ordinates) may be expanded in a series of spherical surface harmonics of the form
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It is established how the rapidity of convergence of such an expansion series depends upon the smoothness of the function f(
) that is being expanded. This provides conditions under which the expansion series of f converges absolutely; asymptotic bounds on the expansion coefficients anm, bnm, are also deduced. Analytical properties are established for a function defined by the sum of a series of surface harmonics, whose coefficients are obtained by modifying the coefficients from the expansion of a given function. This is what is required in many applications. Simple uniform bounds for the functions Pnm(cos
) and their derivatives are also obtained and conditions are deduced under which a series of surface harmonics with generally assigned coefficients converges absolutely; analytical properties of the sum are also established.
