The liquid-gas phase transition and the caloric curve of nuclear matter

A new relativistic mean-…eld model, which reproduces the astronomical observations of neutron stars and the experimental nuclear symmetry energy, is applied to warm nuclear matter. We con…rm that the model also reproduces the critical temperature and the caloric curve in the liquid-gas phase transition of nuclear matter. The recent great experimental progress [1-4] in nuclear multifragmentation reaction has revealed the liquid-gas phase transition of nuclear matter. Its signals are observed in the critical phenomena [5-8], the caloric curve [9,10], the negative heat capacity [11,12] and the bimodality [13]. The phase transition provides valuable information on nuclear equation of state (EOS) at sub-saturation densities. On the other hand, the recent astronomical observations of neutron stars (NSs) provide the information on the EOS at super-saturation densities. In the theoretical point of view it is desirable to reproduce both the EOSs of dilute and dense nuclear matter and both the EOSs of warm and cool nuclear matter simultaneously on the single fundamental model of nuclear system. It has been found recently [14,15] that the reasonable description of NS matter requires the relativistic mean-…eld (RMF) model, which takes into account the …eld-dependent meson-nucleon coupling constants. In this respect, we have developed a new RMF model [16], which reproduces the mass-radius relation of NS [17] and satis…es the standard scenario of NS cooling. Moreover, the model reproduces the density-dependence of nuclear symmetry energy [18-20] at sub-saturation densities. It is therefore worthwhile to investigate the applicability of the model to the liquid-gas phase transition of warm nuclear matter. In Ref. [16] we have introduced the modi…ed scalar and vector vertices of isoscalar meson: I ! (+) (p0) I (+) (p) + ( ) (p0) I ( ) (p) + (+) (p0) I ( ) (p) + ( ) (p0) I (+) (p) = (1 ) = p0 = p+ (1 + )M N 2M N ; (1)