Asymmetric Nuclear Matter in Relativistic Mean-field Models with Isoscalar- and Isovector-meson Mixing

Abstract

Using the relativistic mean-field model with nonlinear couplings between the isoscalar and isovector mesons, we study the properties of isospin-asymmetric nuclear matter. Not only the vector mixing, omega ( mu ) omega ( mu ) rho ( nu ) rho ( nu ), but also the quartic interaction due to the scalar mesons, sigma (2) delta (2), is taken into account to investigate the density dependence of nuclear symmetry energy, E (sym), and the neutron star properties. It is found that the delta meson increases E (sym) at high densities, whereas the sigma-delta mixing makes E (sym) soft above the saturation density. Furthermore, the delta meson and its mixing have a large influence on the radius and tidal deformability of a neutron star. In particular, the sigma-delta mixing reduces the neutron star radius; thus, the present calculation can simultaneously reproduce the dimensionless tidal deformabilities of a canonical 1.4 M (circle dot) neutron star observed from the binary neutron star merger GW170817 and the compact binary coalescence GW190814.