Big-Bang Nucleosynthesis Revisited

The results of an improved calculation of the synthesis of elements during the high-temperature phase of the expansion of big-bang universes is presented. Adoption of the viewpoint (supported by recent evidence) that most of the observed deuterium and helium is of pregalactic origin allows very general constraints to be put on any cosmological model for their production. In fact, most models which differ appreciably from that of the most naive (standard) big-bang are ruled out. Those standard big-bang models in which the present baryon density is (1-3) x 10-31 g agree best with the probable pregalactic abundances of 2H, 3He, and 4He, if the galactic production of 3He is also assumed negligible. It is also shown on very general grounds that the present universal baryon density and average abundance (by mass) of primordial deuterium should be related by p5(T = 2.7 K) X(2H) < 2 x 1O- g . Since no known galactic process can produce a deuterium abundance of X(2H) > 10-6, any detection of interstellar deuterium in this range could be of profound cosmological significance. Subject headings: abundances - cosmology - gravitation - nuclear reactions