Isovector properties of the Gogny interaction

We analyze the properties of the Gogny interaction in homogeneous matter, with special emphasis on the isovector sector. We provide analytical expressions for both the single-particle and the bulk properties of symmetric and asymmetric nuclear matter. We perform an extensive analysis of these properties using eleven parametrizations extracted from the literature. We find that most Gogny interactions have low values for the slope of the symmetry energy, outside the range of empirically extracted values. As a test of extreme isospin dependence, we also study the neutron star mass-radius relations implied by the different Gogny equations of state. Our results call for a more careful fitting procedure of the isovector properties of Gogny functionals.