Influence of density dependence of NNρ coupling on the liquid-gas phase transition in warm asymmetric nuclear matter

In a study of the liquid-gas phase transition in warm asymmetric nuclear matter by means of the FST model, a density-dependent nucleon-nucleon-rho-meson (NNrho) coupling is introduced. It is found that the density dependence of the effective (NNrho) coupling makes the phase transition more complicated than the constant coupling case which is usually assumed. The section of the binodal surface at a fixed temperature may be cut off at a pressure limit p(lim), above which there is no two-phase coexistence. A second-order phase transition taking place in asymmetric nuclear matter below its pressure limit changes to a first-order transition at the pressure limit.