http://arxiv.org/abs/1310.3608
We study the finite temperature and density effects on beta decay rates to compute their contributions to nucleosynthesis. QED type corrections to beta decay from the background are studied in the standard model with massless neutrinos. So we re-examine the electron mass contributions and compute the beta decay rate, helium yield, energy density of the universe as well as the change in neutrino temperature, directly from the first order contribution to the selfmass of electrons during these processes. We express nucleosynthesis parameters as a function of temperature and density in different astronomical systems of interest. In this paper, we notice that the helium abundance at T=m of a cooling universe (0.045%) is higher than the helium abundance of a heating universe (0.031%) indicates that the universe started to produce helium at T>m and stopped after some point at T<m. It is also explicitly shown that the chemical potential in the core of supermassive and superdense stars affect beta decay and their helium abundance but the background contributions is still dependent on relative temperature. We calculate this contribution for Temperatures sufficiently smaller than the electron mass which is smaller than the chemical potential. It has been noticed that the acceptable background contribution are obtained for comparatively larger values of T as temperature plays a role of regulating parameter in an extremely dense system.
Date added: Tue, 15 Oct 13