Relativistic Mean-Field Theory Equation of State of Neutron Star Matter and a Maxwellian Phase Transition to Strange Quark Matter

TL;DR

This paper investigates the equation of state for neutron star matter using relativistic mean-field theory with a delta meson, analyzing phase transitions to strange quark matter via a Maxwellian approach.

Contribution

It introduces the delta meson into the relativistic mean-field model and studies its impact on the phase transition parameters to strange quark matter.

Findings

Including delta meson reduces phase transition pressure.

Delta meson affects nucleon and quark concentrations at transition.

Phase transition characteristics depend on bag model parameters.

Abstract

The equation of state of neutron star matter is examined in terms of the relativistic mean-field theory, including a scalar-isovector $\delta$-meson effective field. The constants of the theory are determined numerically so that the empirically known characteristics of symmetric nuclear matter are reproduced at the saturation density. The thermodynamic characteristics of both asymmetric nucleonic matter and $\beta$-equilibrium hadron-electron $npe$-plasmas are studied. Assuming that the transition to strange quark matter is an ordinary first-order phase transition described by Maxwell's rule, a detailed study is made of the variations in the parameters of the phase transition owing to the presence of a $\delta$-meson field. The quark phase is described using an improved version of the bag model, in which interactions between quarks are accounted for in a one-gluon exchange approximation. The characteristics of the phase transition are determined for various values of the bag parameter within the range $B\in[60,120]$ $MeV/fm^{3}$ and it is shown that including a $\delta$-meson field leads to a reduction in the phase transition pressure $P_{0}$ and in the concentrations $n_{N}$ and $n_{Q}$ at the phase transition point.