Progress on obtaining unified nuclear matter EOSs in RMF models

Xia, Chengjun

In the framework of Thomas-Fermi approximation, we study systematically the EOSs and microscopic structures of nuclear matter in various densities and temperatures. Typical pasta structures (droplet, rod, slab, tube, and bubble) are obtained adopting spherical and cylindrical approximations for Wigner-Seitz cells, where the optimum configurations are fixed by minimizing the free energy. The phase diagrams of nuclear matter are then obtained, which should be useful for understanding the evolutions of neutron stars, supernova dynamics, and binary neutron star mergers.

Interacting ud and uds quark matter at finite densities and quark stars

Xia, Chengjun

The stability and equation of state of quark matter are studied within both two-flavor and (2+1)-flavor Nambu–Jona-Lasinio (NJL) models including the vector interactions. With a free parameter $\alpha$, the Lagrangian is constructed by two parts, the original NJL Lagrangian and the Fierz transformation of it. We find that there is a possibility for both nonstrange and strange matter being absolute stable, depending on the interplay of the confinement with quark vector interaction and the exchange interaction channels. The calculated quark star properties can reconcile with the recently measured mass and radius of PSR J0030+0451 and PSR J0740+6620, as well as the tidal deformability of GW170817. Furthermore, the more strongly-interacting quark matter in the nonstrange stars allows a stiffer equation of state and consequently a higher maximum mass than the strange ones. The sound velocity in strange and nonstrange quark star matter are briefly discussed compared to those of neutron star matter.s