Nuclear Matter And Neutron Star Properties With Consideration Of δ Meson

Neutron stars, as the natural laboratories to test the properties of hadronic matter under extreme conditions, have been one of the hottest topics both in nu-clear physics and astrophysics. In the investigation of neutron stars, searching for the proper equation of state (EOS) was a long-sought goal and central task. Usually, EOS will generate unique mass radius (M-R) relation for neutron stars. However, because the poorly constrained many-body interaction at supranucle-ar densities, there still exists considerable theoretical uncertainty on the EOS. What’s more, the newest researches imply that the M-R relationships given by many models are inconsistent with the observations. During recent decades, many successes have been achieved in describing nuclear properties in the rel-ativistic mean field (RMF) theory. At present, the widely used RMF approach neglects the isovector scalar 8 meson. Recently, a new high-precision density functional DD-MEδ is presented which includes the δmeson, with density-dependent meson-nucleon couplings, and which to a large extent based on mi-croscopic ab initio calculations in nuclear matter.Based on the density-dependent relativistic mean field (RMF) theory, the properties for nuclear matter and neutron stars with the effective interaction DD-MEδ including δ meson and other three interactions DD-ME2, TW99, and PKDD, which neglect δ meson. The influences of the isovector scalar 8 meson on properties of asymmetric nuclear matter at high densities are discussed in de-tail. The results support that the isovector scalar channel can soften the equation of state (EOS) through the effects on the nucleon effective mass and the scalar σ field and impact the behavior of the nuclear matter symmetry energy. Because of the influence on the symmetry energy by δ meson, a larger proton fraction in neutron stars is predicted by the DD-MEδ calculation, which strongly affects the cooling process of the star. The maximum masses of neutron stars given by the DDMEδ calculation is 1.97M⊙ which is in reasonable agreement with PSR J1614-2230 (1.97±0.04 M⊙) and PSR J0348+0432 (2.01±0.04 M⊙). Among all the selected interactions, DD-MEδ gives the smallest radius range. The radius for the 1.4 solar mass neutron star calculated by DD-MEδ is in good agreement with the prediction [Astrophys. J. Lett.765, L5 (2013)] according to the resent observations.