Primordial Nucleosynthesis

During its hot, dense, early evolution the Universe was a primordial nuclear reactor, synthesizing the light nuclides D, 3He, 4He and 7Li in the first thousand seconds. The presently observed abundances of these relic nuclides provide a unique window on the early Universe. The implications of current observations for cosmology (the universal density of nucleons) and for particle physics (new particles beyond the standard model) will be reviewed. The present data appear to be ...

The current status of big bang nucleosynthesis is summarized. Particular attention is paid to recent observations of He4 and Li7 and their systematic uncertainties. Be and B are also discussed in connection to recent Li7 observations and the primordial Li7 abundance.

In the standard hot big bang nucleosynthesis (BBN) model the primordial abundances of H, H2, He3, He4, and Li7, fix the baryon density of the universe, $\Omega_b$, via the baryon-to-photon ratio, $\eta$, for a given Hubble parameter. Recent observations of Li show that its intrinsic dispersion in metal-poor stars is essentially zero, and the random error in the mean Li abundance is negligible. However, a decreasing trend in the Li abundance towards lower metallicity, plus Li6...

A review of the latest measurements of the primordial abundances of the light nuclei D, 3He, 4He and 7Li is given. We discuss in particular the primordial abundance Yp of 4He as measured in blue compact dwarf galaxies. We argue that the best measurements now give a ``high'' value of Yp along with a ``low'' value of D/H, and that the two independent measurements are consistent within the framework of standard Big Bang nucleosynthesis with a number of light neutrino species Nnu...

The current status of big bang nucleosynthesis is reviewed. Particular attention is given to the degree at which the theory is consistent with the observation of the light element abundances.

WThe current status of big bang nucleosynthesis is reviewed with an emphasis on the comparison between the observational determination of the light element abundances of \D, \he3, \he4 and \li7 and the predictions from theory. In particular, we present new analyses for \he4 and \li7. Implications for physics beyond the standard model are also discussed. Limits on the effective number of neutrino flavors are also updated.

A critical review is given of the current status of cosmological nucleosynthesis. In the framework of the Standard Model with 3 types of relativistic neutrinos, the baryon-to-photon ratio, $\eta$, corresponding to the inferred primordial abundances of deuterium and helium-4 is consistent with the independent determination of $\eta$ from observations of anisotropies in the cosmic microwave background. However the primordial abundance of lithium-7 inferred from observations is ...

Big Bang Nucleosynthesis represents perhaps the first, and still perhaps the most powerful particle-astrophysics connection. As such, it should provide an example for other work in this area. I discuss the current status of standard model BBN predictions and constraints, and then argue that the issue of observational systematic uncertainties is the key feature limiting our ability to constrain theory with observation. Nevertheless, several very important constraints are curre...

Primordial or big bang nucleosynthesis (BBN) is now a parameter free theory whose predictions are in good overall agreement with observations. However, the 7Li calculated abundance is significantly higher than the one deduced from spectroscopic observations. Most solutions to this lithium problem involve a source of extra neutrons that inevitably leads to an increase of the deuterium abundance. This seems now to be excluded by recent deuterium observations that have drastical...

Primordial nucleosynthesis is inevitable during the early evolution of an expanding universe filled with radiation and matter (baryons). However, the precise abundance yields depend sensitively on the baryon density, the radiation content and the early expansion rate. For ``standard" big bang nucleosynthesis (SBBN) only D, $^3$He, $^4$He and $^7$Li are produced in astrophysically interesting abundances which depend on only one ``free" parameter, $\eta = n_{\rm B}/n_{\gamma}$,...