Asymmetric nuclear matter and realistic potentials

The equation of state for asymmetric nuclear matter is presented within the Brueckner-Hartree-Fock (BHF) approach by using recent high-quality soft nucleon-nucleon potentials from next-to-leading order (NLO) up to fifth order (N4LO) of the chiral expansion for the wide range of densities and asymmetry parameter, which are very interesting these days in the heavy-ion collisions and neutron stars. For comparison purposes, the same calculations are performed for Brueckner-Hartree-Fock approach plus two-body density-dependent Skyrme potential which is equivalent to three-body forces. Also the results are compared with the other theoretical models, especially the Brueckner-Hartree-Fock plus threebody forces and the Dirac-Brueckner-Hartree-Fock approaches. Our equation-of-state models are able to reproduce the empirical symmetry energy E-sym and its slope parameter L at the empirical saturation density rho(0) and are compatible with experimental data from collisions between heavy nuclei. The symmetry energy of about 30 MeV is obtained at the saturation nuclear matter density. There is very good agreement between the experimental symmetry energy value and those calculated in the Brueckner-Hartree-Fock approach.