Role of strangeness and isospin in low density expansions of hadronic matter

International audienceWe compare relativistic mean-field models with their low density expansion counterparts used to mimic nonrelativistic models by consistently expanding the baryonic scalar density in powers of the baryonic number density up to O(13/3), which goes two orders beyond the order considered in previous works. We show that, due to the nontrivial density dependence of the Dirac mass, the convergence of the expansion is very slow, and the validity of the nonrelativistic approximation is questionable even at subsaturation densities. In order to analyze the roles played by strangeness and isospin we consider n-Λ and n-p matter separately. Our results indicate that these degrees of freedom play quite different roles in the expansion mechanism and n-Λ matter can be better described by low density expansions than n-p matter in general