Constraining mean-field models of the nuclear matter equation of state at low densities

TL;DR

This paper extends the generalized relativistic mean-field model to accurately describe low-density nuclear matter, incorporating light nuclei and scattering correlations, with applications in astrophysics.

Contribution

It introduces a density-dependent gRMF model that includes bound states and scattering correlations, matching low-density virial EOS and high-density RMF results.

Findings

Model reproduces virial equation of state at low densities

Relativistic effects are significant at astrophysical temperatures

Provides consistency relations linking quasiparticles and scattering data

Abstract

An extension of the generalized relativistic mean-field (gRMF) model with density dependent couplings is introduced in order to describe thermodynamical properties and the composition of dense nuclear matter for astrophysical applications. Bound states of light nuclei and two-nucleon scattering correlations are considered as explicit degrees of freedom in the thermodynamical potential. They are represented by quasiparticles with medium-dependent properties. The model describes the correct low-density limit given by the virial equation of state (VEoS) and reproduces RMF results around nuclear saturation density where clusters are dissolved. A comparison between the fugacity expansions of the VEoS and the gRMF model provides consistency relations between the quasiparticles properties, the nucleon-nucleon scattering phase shifts and the meson-nucleon couplings of the gRMF model at zero density. Relativistic effects are found to be important at temperatures that are typical in astrophysical applications. Neutron matter and symmetric matter are studied in detail.