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

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 twofold: 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.

On the Maximum Mass of Neutron Stars

“…(14) is a maximum maximorum since the assumption of incompressible matter violates causality and special relativity. A more stringent upper limit on the NS mass can be obtained by assuming that at densities above ρ , the EoS is the stiffest possible, [78][79][80][81][82][83][84][85][86][87][88] with dP/dρ = c 2 :…”

Neutron stars: From the inner crust to the core with the (extended) Nambu–Jona-Lasinio model

“…4, we compare the symmetric nuclear matter pressure to experimental results obtained from collective flow data in heavy-ion collisions [50] and from the KaoS experiment [51][52][53][54]. The left panel only contains nucleonic EOS.…”

Interplay between the symmetry energy and the strangeness content of neutron stars

“…It will be shown not only that the presence of the strange mesons σ * and φ is important to give rise to a hard hyperonic EOS at large densities as already shown in [3,5], but also that the density dependence of the EOS at 2-3 times saturation density has noticeable effects on the star properties. In [18], the authors study the implication of a soft EOS, as obtained from kaon production in heavy-ion collisions at these same densities [19], on the properties of compact star.…”