1507.05022
Efficient evaluation of cosmological angular statistics
Assassi, Simonović, Zaldarriaga
Angular statistics of cosmological observables are hard to compute. The main difficulty is due to the presence of highly-oscillatory Bessel functions which need to be integrated over. In this paper, provide a simple and fast method to compute the angular power spectrum and bispectrum of any observable. The method is based on using an FFTlog algorithm to decompose the momentum-space statistics onto a basis of power-law functions. For each power law, the integrals over Bessel functions have a simple analytical solution. This allows efficient evaluations of these integrals, independently of the value of the multipole ell. Apply this general method to the galaxy, lensing and CMB temperature angular power spectrum and bispectrum.
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