# Efficient Evaluation of Cosmological Angular Statistics

Research paper by Valentin Assassi, Marko Simonović, Matias Zaldarriaga

Indexed on: 14 May '17Published on: 14 May '17Published in: arXiv - Astrophysics - Cosmology and Nongalactic Astrophysics

#### Abstract

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, we 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 us to efficiently evaluate these integrals, independently of the value of the multipole $\ell$. We apply this general method to the galaxy, lensing and CMB temperature angular power spectrum and bispectrum.