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, $E_{\mathrm{sym}}$, and the neutron-star properties. It is found that the $\delta$ meson increases $E_{\mathrm{sym}}$ at high densities, whereas the $\sigma$-$\delta$ mixing makes $E_{\mathrm{sym}}$ 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, and, thus, the present calculation can simultaneously reproduce the dimensionless tidal deformabilities of a canonical $1.4M_{\odot }$ neutron star observed from the binary neutron star merger, GW170817, and from the compact binary coalescence, GW190814.

Comments: 11 pages, 14 figures, 2 tables