The quark-hadron phase transition and primordial nucleosynthesis

Abstract

A simple model for the quark-hadron phase transition is constructed based on the bag model for the quark-gluon plasma, the known spectrum of hadronic states, and elementary statistical techniques. The most important parameters are the bag constant and the fraction of the volume of the universe which is in high baryon density regions left over from the decoupling of the quark-gluon plasma. Primordial nucleosynthesis is investigated in this parameter space. For high coexistence temperatures characteristic of a large bag constant, it is found that the isothermal baryon number fluctuations are small and standard big bang nucleosynthesis is recovered. For coexistence temperatures not much greater than those derived from the standard MIT bag model, it is confirmed that isothermal baryon inhomogeneities lead to prediction of primordial nucleosynthesis consistent with most light-element abundances, even with Omega(b) = 1, but with an overproduction of Li-7.