Diffusion coefficients and inhomogeneous big-bang nucleosynthesis

Abstract

We study the effects of recently calculated baryon diffusion coefficients on the yields of primordial light elements in baryon-inhomogeneous big-bang models. The new coefficients are an improvement over previously used values in that they go to the correct nonrelativistic limit for neutron-electron scattering and give a more correct numerical value for the nucleon-nucleon scattering contribution. The largest effect of these new coefficients on nucleosynthesis is through neutron-proton scattering. We find that the somewhat larger value for D_np in the present work shifts the optimum separation distance between fluctuations, at which the effects of inhomogeneities are maximized, to slightly larger distance scales. Otherwise, the nucleosynthesis yields derived using these new diffusion coefficients are similar to those obtained previously thereby confirming the robustness of earlier derived constraints.