The liquid–gas phase transition in a variational approach and the role of three-body force

Abstract

The thermal properties of hot baryonic matter and its isospin dependence for a wide range of densities and temperatures have been investigated within the lowest order constrained variational (LOCV) approach by employing the bare two-body interaction AV18 with the inclusion of a phenomenological three-body force (3BF) UIX as well as relativistic corrections (RC). The critical temperature and the liquid–gas (LG) phase transition have been calculated with and without the inclusion of 3BF both in the LOCV and its relativistic expansion, namely (RLOCV) approach. Our results have been compared with other predictions. It turns out that the 3BF gives a repulsive contribution to the equation of state (EOS) which is stronger at higher density and as a consequence reduces the critical temperature of LG phase transition while RC has no special effect on the critical point. The temperature dependence and the isospin dependence of other physical quantities, such as the specific heat capacity, latent heat, entropy, critical exponents, symmetry free energy, incompressibility and the role of UIX 3BF on these quantities have also been studied. At a given temperature, we find a reduction in critical temperature, latent heat, critical asymmetry parameter, and incompressibility when 3BF is added to the bare interaction, while 3BF has no effect on entropy and specific heat capacity, as expected. We observed that the stiffness of density-dependence of symmetry free energy affects on the critical point of LG phase transition. Stiffer symmetry free energy has a smaller critical temperature. Also, by including 3BF, the critical point is obtained in KBT=17.1MeV at 0.06 fm−3 , and the maximum value of latent heat is found in the range ∼31.8MeV.