Model-independent predictions of big bang nucleosynthesis

We derive constraints from standard (with N-nu = 3) BBN arising solely from two cosmologically produced nuclides, He-4 and Li-7, from which the extrapolation to primordial abundances is straightforward. The abundances of D and He-3 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 He-4 and Li-7, 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 He-4 and Li-7 abundances are also used to predict the primordial abundances D and He-3, which provides an initial condition for their chemical evolution.