The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes
Apr, 201135 pages
Published in:
- JCAP 07 (2011) 034
e-Print:
- 1104.2933 [astro-ph.CO]
Report number:
- CERN-PH-TH-2011-082,
- LAPTH-010-11
Citations per year
Abstract: (arXiv)
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 newly released 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 baryon-photon tight-coupling approximation which can be set to first order, second order or to a compromise between the two; an ultra-relativistic fluid approximation which had not been implemented in public distributions before; and finally a radiation streaming approximation taking reionisation into account.Note:
- 35 pages, 10 figures, 5 tables. Ultra-relativistic fluid approximation better justified in a new Appendix B. Version accepted in JCAP. Code available at http://class-code.net
References(14)
Figures(0)