CLASS: Cosmic Linear Anisotropy Solving System
Abstract
Boltzmann codes are used extensively by several groups for constraining cosmological parameters with Cosmic Microwave Background and Large Scale Structure data. This activity is computationally expensive, since a typical project requires from 10'000 to 100'000 Boltzmann code executions. The code CLASS (Cosmic Linear Anisotropy Solving System) incorporates improved approximation schemes leading to a simultaneous gain in speed and precision. We describe here the three approximations used by CLASS for basic LambdaCDM models, namely: a baryonphoton tightcoupling approximation which can be set to first order, second order or to a compromise between the two; an ultrarelativistic fluid approximation which had not been implemented in public distributions before; and finally a radiation streaming approximation taking reionisation into account.
 Publication:

Astrophysics Source Code Library
 Pub Date:
 June 2011
 Bibcode:
 2011ascl.soft06020B
 Keywords:

 Software