Asymmetric Nuclear Matter and Neutron Star Properties in Relativistic ab initio Theory in the Full Dirac Space

The long-standing controversy about the isospin dependence of the effective Dirac mass in ab initio calculations of asymmetric nuclear matter is clarified by solving the relativistic Brueckner-Hartree-Fock equations in the full Dirac space. The symmetry energy and its slope parameter at the saturation density are $E_{\text{sym}}(\rho_0)=33.1$ MeV and $L=65.2$ MeV, in agreement with empirical and experimental values. Further applications predict the neutron star radius $R_{1.4M_\odot}\approx 12$ km and the maximum mass of a neutron star $M_{\text{max}}\leq 2.4M_\odot$.