Soft nuclear equation-of-state from heavy-ion data and implications for compact stars

TL;DR

This paper uses heavy-ion collision data indicating a soft nuclear equation-of-state to explore implications for neutron star properties, including mass limits and the density dependence of nuclear symmetry energy.

Contribution

It applies heavy-ion collision results to constrain the nuclear equation-of-state and derive limits on neutron star masses and radii.

Findings

Heavy-ion data suggest a soft nuclear EoS up to 2-3 times nuclear saturation density.

Constraints from data and causality limit neutron star mass to about three solar masses.

Potential to inform neutron star radius measurements and nuclear symmetry energy behavior.

Abstract

Measurements of kaon production at subthreshold energies in heavy-ion collisions point to a soft nuclear equation-of-state for densities up to 2-3 times nuclear matter saturation density. We apply these results to study the implications on compact star properties, especially in the context of the recent measurement of the two solar mass pulsar PSR J1614-2230. The implications are two-fold: Firstly, the heavy-ion results constrain nuclear matter at densities relevant to light neutron stars. Hence, a radius measurement could provide information about the density dependence of the symmetry energy which is a crucial quantity in nuclear physics. Secondly, the information on the nucleon potential obtained from the analysis of the heavy-ion data can be combined with restrictions from causality on the nuclear equation-of-state. From this we can derive a limit for the highest allowed compact star mass of three solar masses.