ABSTRACT
This chapter introduces a broad collection of different competing models for the equation of state of superdense neutron matter. Some of these models describe conventional neutron star matter in phase equilibrium with quarks. Others account for meson condensates or variations in the hyperon population depending on the underlying many-body method. To derive the equation of state for the many-body approximation for the sake of illustration, a mathematical route different from the one adopted for the HF case. The calculation of energy density and pressure of a free, relativistic lepton gas may serve as a further simple case to demonstrate the principal ideas behind the Green function technique. The self-consistent nuclear matter incompress-ibilities at saturation obtained for the T-matrix calculations as well as those based on non-relativistic nucleon-nucleon potentials are relatively small in comparison to those associated with relativistic Hartree or Hartree-Fock.
