The expansion in Gegenbauer polynomials: A simple method for the fast computation of the Gegenbauer coefficients

  • Authors:
  • Enrico De Micheli;Giovanni Alberto Viano

  • Affiliations:
  • IBF - Consiglio Nazionale delle Ricerche, Via De Marini, 6, 16149 Genova, Italy;Facoltí di Scienze Matematiche, Fisiche e Naturali - Universití di Genova, Via Dodecaneso, 33, 16146 Genova, Italy

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2013

Quantified Score

Hi-index 31.45

Visualization

Abstract

We present a simple and fast algorithm for the computation of the Gegenbauer transform, which is known to be very useful in the development of spectral methods for the numerical solution of ordinary and partial differential equations of physical interest. We prove that the coefficients of the expansion of a function f(x) in Gegenbauer (also known as ultraspherical) polynomials coincide with the Fourier coefficients of a suitable integral transform of the function f(x). This allows to compute N Gegenbauer coefficients in O(Nlog"2N) operations by means of a single Fast Fourier Transform of the integral transform of f(x). We also show that the inverse Gegenbauer transform is expressible as the Abel-type transform of a suitable Fourier series. This fact produces a novel algorithm for the fast evaluation of Gegenbauer expansions.