Model-Independent Predictions of Big Bang Nucleosynthesis

We derive constraints from standard (with $N_\nu = 3$) BBN arising solely from two cosmologically produced nuclides, \he4 and \li7, from which the extrapolation to primordial abundances is straightforward. The abundances of D and \he3 are at present only inferred from their solar and local interstellar medium values using models of galactic chemical evolution. However, our knowledge of chemical evolution suffers from large uncertainties, and so it is of use to take an approach which minimizes the reliance on chemical evolution in determining the consistency of BBN. Using only the data on \he4 and \li7, and reasonable estimates of possible systematic errors in their abundance determinations, concordance is found if the baryon-to-photon ratio lies in the range $1.4 < 10^{10} \eta < 3.8$ (95\% CL). The \he4 and \li7 abundances are also used to predict the primordial abundances D and \he3, which provides an initial condition for their chemical evolution.