Liquid-gas and superconducting phase transitions of nuclear matter calculated with real time Green’s function methods and Skyrme interactions

Abstract

Real-time finite temperature Green’s function methods with pair cutoff approximations are applied to the calculation of the equation of state of symmetric nuclear matter. The liquid-gas and the superconducting second-order phase transitions of nuclear matter are studied using, respectively, the normal and abnormal pair cutoff approximations. Several versions of the Skyrme effective interactions are employed. Significant differences are found between the pressure-density isotherms at finite temperature given by different Skyrme interactions, although they give quite similar ground state nuclear matter properties. The critical temperatures kBTc(1) for the liquid-gas phase transition given by various Skyrme interactions range from ∼15 to ∼20 MeV. A strong dependence of kBTc(1) on the combination 3t1+5t2, t1 and t2 being two parameters of the Skyrme interaction, is observed. For nuclear matter at normal density, nonvanishing energy gap is obtained only for the Skyrme interactions SkI and SkVI. The critical temperatures for the superconducting second-order phase transitions for these two cases are, respectively, 0.5 and 0.345 MeV. Dependence of the energy gap on the nuclear matter density is discussed.

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