BIG-BANG NUCLEOSYNTHESIS AND A NEW APPROACH TO GALACTIC CHEMICAL EVOLUTION

Big bang production of deuterium is the best indicator of the baryon density; however, only the present abundance of D is known (and only locally) and its chemical evolution is intertwined with that of He-3. Because Galactic abundances are spatially heterogeneous, mean chemical-evolution models are not well suited for extrapolating the pre-solar D and He-3 abundances to their primeval values. We introduce a new approach which explicitly addresses heterogeneity by statistically tracing the history of the pre-solar material back to its primeval beginning. We show that the decade-old concordance interval eta approximate to (2-8)x10(-10) based on D and He-3 is well founded.