Big bang nucleosynthesis: Present status

By Richard H. Cyburt, B. Fields, K. Olive, Tsung-Han Yeh. 2015

619 citations recorded by the source corpus.

Big-bang nucleosynthesis (BBN) describes the production of the lightest nuclides via a dynamic interplay among the four fundamental forces during the first seconds of cosmic time. We briefly overview the essentials of this physics, and present new calculations of light element abundances through li6 and li7, with updated nuclear reactions and uncertainties including those in the neutron lifetime. We provide fits to these results as a function of baryon density and of the number of neutrino flavors, N_nu. We review recent developments in BBN, particularly new, precision Planck cosmic microwave background (CMB) measurements that now probe the baryon density, helium content, and the effective number of degrees of freedom, n_eff. These measurements allow for a tight test of BBN and of cosmology using CMB data alone. Our likelihood analysis convolves the 2015 Planck data chains with our BBN output and observational data. Adding astronomical measurements of light elements strengthens the power of BBN. We include a new determination of the primordial helium abundance in our likelihood analysis. New D/H observations are now more precise than the corresponding theoretical predictions, and are consistent with the Standard Model and the Planck baryon density. Moreover, D/H now provides a tight measurement of N_nu when combined with the CMB baryon density, and provides a 2sigma upper limit N_nu < 3.2. The new precision of the CMB and of D/H observations together leave D/H predictions as the largest source of uncertainties. Future improvement in BBN calculations will therefore rely on improved nuclear cross section data. In contrast with D/H and he4, li7 predictions continue to disagree with observations, perhaps pointing to new physics.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/381196bf9f71f34fd4f4186d925f1285093ab4b5

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Citations in the corpus

One Percent Determination of the Primordial Deuterium Abundance (2017, methodology): “…as gas is cycled through generations of stars (Dvorkin et al. 2016; van de Voort et al. 2017, and the comprehensive list of references provided by Cyburt et al. 2016); (2) The relative ionization of deuterium and hydrogen in neutral gas (Savin 2002; Cooke & Pettini 2016); and (3) The…”
KiDS-450: testing extensions to the standard cosmological model (2016, methodology): “…the conservative prior 0.013 < bh2 < 0.033 on the baryon density [motivated by the big bang nucleosynthesis (BBN) constraints in Burles, Nollett & Turner 2001; Olive & Particle Data Group 2014; Cyburt et al. 2016 and 0.4 < h < 1.0 on the dimensionless Hubble constant (which is a derived parameter).”
The Simons Observatory: science goals and forecasts (2018, background): “Big bang nucleosynthesis Big bang nucleosynthesis is the process by which light elements were formed in the early universe (for reviews see Patrignani et al. 2016; Cyburt et al. 2016).”
Precision big bang nucleosynthesis with improved Helium-4 predictions (2018, methodology): “However, Aver et al. (2015) (see also Cyburt et al. (2016)), starting from the same observational data made a stricter selection, based, in particular on goodness of fit for the emission model of each object.”
Non-Gaussianity and the induced gravitational wave background (2021, background): “Moreover, the abundances of light elements are insensitive to the state of the Universe prior to BBN and neutrino decoupling (before redshift z ∼ 1010) [12].”
Origin of the heaviest elements: The rapid neutron-capture process (2019, background): “Presently we know that of the natural elements/isotopes only H, He and Li originate in the Big Bang, with problems remaining in understanding the abundance of Li (Cyburt et al., 2016; Pitrou et al., 2018).”
Elucidating ΛCDM: Impact of Baryon Acoustic Oscillation Measurements on the Hubble Constant Discrepancy (2017, methodology): “Closed contours in the Ωbh2−Neff plane can be obtained from combining estimates of the primordial D/H and 4He abundance (e.g., review by Cyburt et al. 2016, and references therein).”
De re metallica: the cosmic chemical evolution of galaxies (2018, background): “…elements While primordial nucleosynthesis accounts for the origin of hydrogen, deuterium, the majority helium and a small fraction of lithium (e.g., Cyburt et al., 2016), all other elements are produced by stellar nucleosynthesis or by the explosive burning and photodisintegration associated with…”