2011/12/12 by Kenneth M. Nollett, G. P. Holder, Nollett, Kenneth M. +1
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Nuclear Theory (nucl-th) #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.1112.2683
openalex publication_date 2011/12/12 · openalex created_date 2022/08/27 · openalex updated_date 2026/07/28
We present constraints on the number of relativistic species from a joint\nanalysis of cosmic microwave background (CMB) fluctuations and light element\nabundances (helium and deuterium) compared to big bang nucleosynthesis (BBN)\npredictions. Our BBN calculations include updates of nuclear rates in light of\nrecent experimental and theoretical information, with the most significant\nchange occuring for the d(p,gamma)3He cross section. We calculate a likelihood\nfunction for BBN theory and observations that accounts for both observational\nerrors and nuclear rate uncertainties and can be easily embedded in\ncosmological parameter fitting. We then demonstrate that CMB and BBN are in\ngood agreement, suggesting that the number of relativistic species did not\nchange between the time of BBN and the time of recombination. The level of\nagreement between BBN and CMB, as well as the agreement with the standard model\nof particle physics, depends somewhat on systematic differences among\ndeterminations of the primordial helium abundance. We demonstrate that\ninteresting constraints can be derived combining only CMB and D/H observations\nwith BBN theory, suggesting that an improved D/H constraint would be an\nextremely valuable probe of cosmology.\n