Soft nuclear equations of state for super-massive neutron star

Two new nuclear equations of state (EOSs) are proposed and are applied to neutron star (NS). They predict the incompressibilitiesK0 = 179MeV and 230MeV, respectively. The density dependencies of nuclear symmetry energies are consistent with the recent analyses of heavy-ion reactions. We can reproduce the recently observed super-massive NS of MG > 2:5M , the mass-radius relation of EXO 0748-676 and the large radius R > 13km of RX J1856.5-3754. No direct URCA in NS is consistent with the standard scenario of NS cooling. Because most of modern EOSs of NS matter cannot satisfy all these constraints, our EOSs are excellent. Nuclear equation of state (EOS) is a long-standing subject in nuclear physics. Recently, we have new insights into its isovector part from the progress in terrestrial experiments of heavy-ion reactions and astronomical observations of neutron stars (NSs). Especially, information [1-8] on the density dependence of nuclear symmetry energy is important. It plays a signi…cant role [9-11] in determining proton fraction in the core of NS and radius of NS. The former is an essential ingredient in the possibility of the direct URCA cooling in NS. According to the standard scenario of NS cooling, the direct URCA process is forbidden and so the proton fraction is severely constrained. Consequently, nuclear symmetry energy is also constrained. The symmetry energy Es( B) can be expanded [8,12] around the nuclear saturation density B0 = 0:16fm : Es ( B) = Es ( B0) + L 3 B B0