Thermal properties of hot and dense matter with finite range interactions

TL;DR

This paper investigates the thermal properties of hot, dense nuclear matter using models with finite-range interactions, comparing them to zero-range models, and examines implications for astrophysical phenomena like neutron stars and supernovae.

Contribution

It introduces a finite-range interaction model that better captures thermal and flow properties of dense matter, contrasting it with traditional zero-range models.

Findings

Finite-range interactions influence thermal state variables.

Differences in specific heats between models are significant.

Thermal and adiabatic indices vary notably at sub-saturation densities.

Abstract

We explore the thermal properties of hot and dense matter using a model that reproduces the empirical properties of isospin symmetric and asymmetric bulk nuclear matter, optical model fits to nucleon-nucleus scattering data, heavy-ion flow data in the energy range 0.5-2 GeV/A, and the largest well-measured neutron star mass of 2 $\rm{M}_\odot$. Results of this model which incorporates finite range interactions through Yukawa type forces are contrasted with those of a zero-range Skyrme model that yields nearly identical zero-temperature properties at all densities for symmetric and asymmetric nucleonic matter and the maximum neutron star mass, but fails to account for heavy-ion flow data due to the lack of an appropriate momentum dependence in its mean field. Similarities and differences in the thermal state variables and the specific heats between the two models are highlighted. Checks of our exact numerical calculations are performed from formulas derived in the strongly degenerate and non-degenerate limits. Our studies of the thermal and adiabatic indices, and the speed of sound in hot and dense matter for conditions of relevance to core-collapse supernovae, the thermal evolution of neutron stars from their birth and mergers of compact binary stars reveal that substantial variations begin to occur at sub-saturation densities before asymptotic values are reached at supra-nuclear densities.