2003/07/31 by Greg Huey, Richard H. Cyburt, Benjamin D. Wandelt
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #astro-ph
paper · pdf · doi:10.1103/physrevd.69.103503
published as Phys.Rev.D69:103503,2004 · 7 pages, 3 color figures made minor changes to bring inline with journal version
openalex publication_date 2004/05/12 · arxiv created 2004/11/02 · arxiv updated 2009/12/01 · openalex created_date 2020/05/29 · openalex updated_date 2026/07/28
Big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) are two major pillars of cosmology. Standard BBN accurately predicts the primordial light element abundances (4He, D, 3He and 7Li), depending on one parameter, the baryon density. Light element observations are used as a baryometer. The CMB anisotropies also contain information about the content of the Universe which allows an important consistency check on the big bang model. In addition CMB observations now have sufficient accuracy to not only determine the total baryon density, but also resolve its principal constituents H and 4He. We present a global analysis of all recent CMB data, with special emphasis on the concordance with BBN theory and light element observations. We find \ensuremathΩBh2=0.0250_\ensuremath-0.0026+0.0019 and Yp=0.250_\ensuremath-0.014+0.010 (fraction of baryon mass as 4He) using CMB data alone, in agreement with 4He abundance observations. The determination of Yp allows us to constrain the relativistic degrees of freedom during BBN, measured through the effective number of light neutrino species, N_\ensuremathν,eff=3.02_\ensuremath-0.79+0.85, in accord with the standard model of particle physics. With this concordance established we show that the inclusion of standard, N_\ensuremathν,eff\ensuremath≡3, BBN theory priors significantly reduces the volume of parameter space. In this case, we find \ensuremathΩBh2=0.0245_\ensuremath-0.0028+0.0015 and Yp=0.2493_\ensuremath-0.0010+0.0007. We also find that the inclusion of deuterium abundance observations reduces the Yp and \ensuremathΩBh2 ranges by a factor of \ensuremath∼2. Further light element observations and CMB anisotropy experiments will refine this concordance and sharpen BBN and the CMB as tools for precision cosmology.