TITLE:
Nucleosynthesis in Hot and Dense Media
AUTHORS:
Samina S. Masood
KEYWORDS:
Nucleosynthesis; Beta Decay; Compact Stars; Hot and Dense Media
JOURNAL NAME:
Journal of Modern Physics,
Vol.5 No.5,
March
31,
2014
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 percent) is higher than the corresponding contribution to
helium abundance of a heating universe (0.031 percent) 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 in the presence of a high concentration
of charged fermions. 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. We calculate the hot and dense background contributions for m = T = μ.
It has been noticed that temperature plays a role in regulating parameter in an
extremely dense systems. Therefore, for extremely dense systems, temperature
has to be large enough to get the expected value of helium production in the
stellar cores.