Thermal quasiparticle random-phase approximation calculations of stellar electron capture rates with the Skyrme effective interaction
Abstract
A microscopic thermodynamically consistent approach is applied to compute electron capture (EC) rates and cross sections on nuclei in hot stellar environments. The cross section calculations are based on the Donnelly-Walecka multipole expansion method for treatment of semi-leptonic processes in nuclei. To take into account thermal effects, we express the electron capture cross section in terms of temperature- and momentum-dependent spectral functions for respective multipole charge-changing operators. The spectral functions are computed by employing the self-consistent thermal quasiparticle RPA (TQRPA) with the Skyrme effective interaction. Three different Skyrme parametrizations (SkM, SGII and SLy4) are used to investigate thermal effects on EC for Fe and Ni. For Fe, the impact of thermally unblocked GT transitions on EC is discussed and the results are compared with those from shell-model calculations. In particular, it is shown that for some temperature and density regimes the TQRPA rates exceed the shell-model rates due to violation of the Brink-Axel hypothesis within the TQRPA. For neutron-rich Ni the full momentum-dependence of multipole transition operators is considered and it is found that not only thermally unblocked allowed transitions but also thermally unblocked first-forbidden and transitions favour EC.
Keywords
Cite
@article{arxiv.1903.08418,
title = {Thermal quasiparticle random-phase approximation calculations of stellar electron capture rates with the Skyrme effective interaction},
author = {Alan A. Dzhioev and A. I. Vdovin and Ch. Stoyanov},
journal= {arXiv preprint arXiv:1903.08418},
year = {2019}
}