Nucleosynthesis in Hot and Dense Media

TL;DR

This paper investigates how finite temperature and density influence beta decay rates and nucleosynthesis, emphasizing QED corrections, electron self-mass effects, and their impact on helium abundance in the early universe and dense stars.

Contribution

It provides a detailed analysis of thermal and density effects on beta decay and nucleosynthesis, including explicit calculations of helium abundance variations and the role of temperature and chemical potential.

Findings

Thermal contribution to helium abundance is higher in cooling universe.

Helium abundance varies with temperature and background fermions.

Temperature regulates beta decay effects in dense astrophysical environments.

Abstract

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 hot and dense background are estimated in terms of the statistical corrections to the self-mass of an electron. For this purpose, we re-examine the hot and dense background contributions to the electron mass and compute its effect to the beta decay rate, helium yield, energy density of the universe as well as the change in neutrino temperature from the first order contribution to the self-mass of electrons during these processes. We explicitly show that the thermal contribution to the helium abundance at T = m of a cooling universe 0.045 % is higher than the corresponding contribution to helium abundance of a heating universe 0.031% due to the existence of hot fermions before the beginning of nucleosynthesis and their absence after the nucleosynthesis, in the early universe. Thermal contribution to helium abundance was a simple quadratic function of temperature, before and after the nucleosynthesis. However, this quadratic behavior was not the same before the decoupling temperature due to weak interactions; so the nucleosynthesis did not even start before the universe had cooled down to the neutrino decoupling temperatures and QED became a dominant theory. 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 depend on the ratio between temperature and chemical potential and not the chemical potential or temperature only. It has been noticed that temperature plays a role of regulating parameter in an extremely dense systems.