The Cosmic Linear Anisotropy Solving System (CLASS). Part II: Approximation schemes

被引:1717
作者
Blas, Diego [1 ]
Lesgourgues, Julien [1 ,2 ,3 ]
Tram, Thomas [2 ,4 ]
机构
[1] Ecole Polytech Fed Lausanne, Inst Theorie Phenomenes Phys, CH-1015 Lausanne, Switzerland
[2] CERN, Div Theory, CH-1211 Geneva 23, Switzerland
[3] Univ Savoie, CNRS, LAPTh, F-74941 Annecy Le Vieux, France
[4] Univ Aarhus, Dept Phys & Astron, DK-8000 Aarhus C, Denmark
关键词
CMBR theory; power spectrum; PERTURBATION;
D O I
10.1088/1475-7516/2011/07/034
中图分类号
P1 [天文学];
学科分类号
070403 [天体物理学];
摘要
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 104 to 105 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 Lambda CDM 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.
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页数:33
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