Inhomogeneous Primordial Nucleosynthesis: Coupled Nuclear Reactions and Hydrodynamic Dissipation Processes

Abstract

We present a detailed study of inhomogeneous Big Bang nucleosynthesis where, for the first time, nuclear reactions are coupled to all significant fluctuation dissipation processes. Theses processes include neutrino heat transport, baryon diffusion, photon diffusive heat transport, and hydrodynamic expansion with photon-electron Thomson drag. Light element abundance yields are presented for broad ranges of initial amplitudes and length scales for spherically condensed fluctuations. The $^2$H, $^3$He, $^4$He, and $^7$Li nucleosynthesis yields are found to be inconsistent with observationally inferred primordial abundances for all but very narrow ranges of fluctuation characteristics. Rapid hydrodynamic expansion of fluctuations late in the nucleosynthesis epoch results in significant destruction of $^7$Li ($^7$Be) only if the baryonic conytribution to the closure density ($Ω_b$) is less than or comparable to the upper limit on this quantity from homogeneous Big Bang nucleosynthesis. This implies that $^7$Li overproduction will peclude an increase on the upper limit for $Ω_b$ for any inhomogeneous nucleosynthesis scenarios employing spherically condensed fluctuations.