Beta equilibrium under neutron star merger conditions

Mark G. Alford, Alexander Haber, Steven P. Harris, Ziyuan Zhang

Published 2021-08-06Version 1

We calculate the isospin chemical potential that is required for beta equilibrium in nuclear matter under neutron star merger conditions, in the temperature range 1 MeV < T < 5 MeV. We improve on previous work by using a consistent description of nuclear matter based on the IUF and SFHo relativistic mean field models. This includes using relativistic dispersion relations for the nucleons, which we show is essential in these models. We find that the isospin chemical potential can be of order 10 to 20 MeV, and plays an important role in the correct calculation of Urca rates, which can be wrong by factors of 10 or more if it is neglected.