Fine tuning in an effective field based relativistic mean field model, and properties of neutron-rich matter

Properties of symmetric nuclear matter and neutron-rich matter predicted by effective field based relativistic mean field parameter sets are compared to those presented in a recent analysis of nuclear giant monopole resonance and isospin diffusion data and a study of the neutron skin of finite nuclei, as well as some selected observational data of neutron stars. Motivated by the fact that none of the published parameter sets of this model is simultaneously consistent with all previously mentioned constraints, an improvement not only in the isovector sector but also in isoscalar sector of this model is proposed. The properties of symmetric nuclear matter and neutron-rich matter, as well as some basic properties of static neutron stars predicted by the proposed parameter set (G2(**)), are discussed.