Nuclear equation of state at high density and the properties of neutron stars

Abstract

We discuss the relativistic nuclear equation of state (EOS) using a relativistic transport model in heavy-ion collisions. From the baryon flow for Au + Au systems at SIS to AGS energies and above we find that the strength of the vector potential has to be reduced moderately at high density or at high relative momenta to describe the flow data at 1-10 A GeV. We use the same dynamical model to calculate the nuclear EOS and then employ this to calculate the gross structure of the neutron star considering the core to be composed of neutrons with an admixture of protons, electrons, muons, sigmas and lambdas at zero temperature. We then discuss these gross properties of neutron stars such as maximum mass and radius in contrast to the observational values.

Complete relativistic equation of state for neutron stars

“…We solve the coupled equations (3)- (7), (8), and (11) self-consistently at a given baryon density n B . The total energy density and pressure of the uniform matter are given by…”

“…2 we show the fraction of species i, Y i = n i /n B , as a function of the total baryon density n B . The composition of uniform neutron star matter is calculated by solving the coupled equations (3)- (7), (8), and (11). The threshold density for a hyperon species is determined not only by its charge and mass but also by the meson mean fields, which are shown in Fig.…”

“…There are a few works based on non-relativistic models describing the EOS at low densities where the heavy nuclei exist [4][5][6]. Most studies of neutron stars are using the composite EOS, which is constructed by connecting the EOS at high densities to the one at low densities [7][8][9]. Even though the EOS at high densities are based on various relativistic many body theories, it has to be combined with some non-relativistic EOS at low densities.…”

Equation of state in hybrid stars and the stability window of quark matter

“…In literature, there is another successful method called relativistic mean-field (RMF) theory. It is a powerful tool in describing various aspects of nuclear physics, such as the properties of nuclear matter, finite nuclei, and neutron stars, as well as the dynamics of heavyion collisions [29,30]. Recently, the model has been extended to include the density-dependent meson-nucleon coupling constant in finite nuclei [31] and nuclear matter [25,32].…”