PRODUCTION OF THE LIGHT-ELEMENTS IN PRIMORDIAL NUCLEOSYNTHESIS

The abundances of the light nuclides 9Be, 10B, and 11B are reexamined in the contexts of the standard model of primordial nucleosynthesis, in which the density of the universe is assumed to be uniform, and of the nonuniform density model, in which density fluctuations are allowed. In these calculations, two reactions not usually included in primordial nucleosynthesis models have been included: 7Li(3H, n)9Be and 9Be(3H, n)11B. Wide ranges of the parameters associated with the nonuniform density model were spanned; the results show that considerably higher abundances of 9Be, 10B, and 11B are produced in that model than in the standard model for most values of the parameters associated with the former model. Furthermore, a study of the galactic chemical evolution of those nuclides which considers all their production mechanisms shows that their abundances depend strongly on those mechanisms. However, measurement of the time dependence of their abundances, together with that of 7Li, might resolve the present controversy surrounding the 7Li abundance, and provide a test of primordial nucleosynthesis models as well. In our study of the galactic chemical evolution of 9Be, 10B, and 11B since the time of primordial nucleosynthesis, explicit note is made of the factors which have the largest uncertainties. Although the allowed ranges are found to be large, observational limits on 9Be, 10B, and 11B are approaching the level needed to provide a definitive test of the predictions of the two primordial nucleosynthesis models.