Neutron star properties and the relativistic nuclear equation of state of many-baryon matter

Abstract

A relativistic model of baryons interacting via the exchange of σ-, ω-, π- and ρ-mesons (scalar-vector-isovector (SVI) theory) is used to describe the properties of both dense and superdense matter. For the theoretical frame, we used the temperature-dependent Green's function formalism. The equation of state (EOS) is calculated for nuclear as well as neutron matter in the Hartree (H) and Hartree-Fock (HF) approximation. The existence of phase transitions has been investigated. The isotherms of pressure as a function of density show for nuclear matter a critical temperature of about T c HF = 16.6 MeV. (As in the usual scalar-vector (SV) theory, the phase transition is absent for neutron matter. A phase transition of both many-baryon systems in the high-pressure and high-density region, which has been found within the SV many-baryon theory, appears in the SVI theory too. The calculated maximum stable masses of neutron stars depend on (1) the underlying parameter set and/or (2) on the chosen approximation (i.e., H, HF; SV-, SVI theory, respectively). Hartree calculations lead to amass stability limit of M max H ⩽ 2.87 M ⊙ ( M max H ⩽ 2.44 M ⊙ when hyperons are taken into account). For the HF calculations we obtained M max HF ⩽ 3.00 M ⊙ ( M max HF ⩽2.85 M ⊙). The corresponding maximum radii are (same notation as above) R H ⩽ 13.2 km ( R H ⩽ 11.8 km), R HF ⩽ 14.0 km ( R HF 0 13.94km). The influence of the approximations, parameter sets and hyperons on the neutron star's moment of inertia is exhibited.