Nuclear Reactions in Inhomogeneous Cosmologies

Abstract

This paper presents additions to the standard nuclear reaction network which are necessary for investigations of primordial nucleosynthesis in inhomogeneous cosmological models. Also presented are the reaction rates associated with these new reactions, the use of these rates may help remove the ambiguity of whether results reported by different groups are, to some extent, an artifact of the different reaction networks employed. It is stressed that many of these reactions play important roles in the nucleosynthesis, but their rates are poorly determined and thus deserve further experimental study. Using the reaction network of Malaney and Fowler (1987, 1988) supplemented by the reactions presented here, it is shown that the production of ⁹Be in inhomogeneous models is strongly dependent on the density contrast R, and on the high-density volume fraction f _υ. Consequently, observations of ⁹Be in stars could lead to vital information on the value of these crucial, but poorly determined, parameters. It is concluded that ⁹Be may be used as a possible indicator of inhomogeneity at the time of nucleosynthesis only for a certain range of f _υ R. For an Ω _b = 1 universe the appropriate range would be f _υ R ≳ 10. Ω _b is the ratio of the universal baryon (b) density to the “critical” density between an open and closed universe which can be calculated from Hubble’s constant (H ₀). For H ₀ = 58 km s^-1 Mpc^-1 the critical density now is 6.3 × 10^-30 g cm^-3 (Fowler 1987).