Nuclear Equation of State for Compact Stars and Supernovae

Abstract

The equation of state (EoS) of hot and dense matter is a fundamental input to describe static and dynamical properties of neutron stars, core-collapse supernovae and binary compact-star mergers. We review the current status of the EoS for compact objects, that have been studied with both ab-initio many-body approaches and phenomenological models. We limit ourselves to the description of EoSs with purely nucleonic degrees of freedom, disregarding the appearance of strange baryonic matter and/or quark matter. We compare the theoretical predictions with different data coming from both nuclear physics experiments and astrophysical observations. Combining the complementary information thus obtained greatly enriches our insight into the dense nuclear matter properties. Current challenges in the description of the EoS are also discussed, mainly focusing on the model dependence of the constraints extracted from either experimental or observational data, the lack of a consistent and rigorous many-body treatment at zero and finite temperature of the matter encountered in compact stars (e.g. problem of cluster formation and extension of the EoS to very high temperatures), the role of nucleonic three-body forces, and the dependence of the direct URCA processes on the EoS.

Hybrid equation of state approach in binary neutron-star merger simulations

“…In particular, the nuclear incompressibility K = 245 MeV turns out to be compatible with the currently acceptable range of 240 ± 20 MeV [31], which agrees with that predicted from the giant monopole resonances. Moreover, the new parameterization ensures that the symmetry energy at saturation density J = 32.8 MeV is well within the empirical range 28.5 − 34.9 MeV [32], and that the neutron-star maximum mass M TOV = 2.06 M is (marginally) compatible with the currently strongest observational constraint M > 2.14 +0.10 −0.09 M [33]. As an illustration of the properties of these two temperature-dependent EOSs, Fig.…”

Ab initio constraints on thermal effects of the nuclear equation of state

“…We thus find important contributions to the effective mass beyond the Hartree-Fock level or mean-field approximation, and that a full description of the effective mass, as given by Eq. (13), is important to describe thermal effects for the nuclear EOS and to reproduce the behavior of the thermal index.…”

“…In view of the recent detection of a gravitational-wave signal from the merger of two neutron stars [9], it is timely for theoretical studies to provide accurate results to meet the needs for correct interpretation of observational outcomes. Apart from the complexity in solving the equations of relativistic hydrodynamics, the modeling of mergers needs to be improved regarding the knowledge of the nuclear matter EOS [10][11][12][13][14]. This is caused by the challenges in understanding the properties of nuclear interactions and dense matter, which are governed by the theory of quantum chromodynamics (QCD).…”

Quantum Skyrmion crystals and the symmetry energy of dense matter

“…the slope and curvature of the symmetry energy at saturation, respectively. The symmetry energy at saturation is well constrained (S 0 ∼ 30MeV) by nuclear experiments [24], but the values of the slope and higher order coefficients are still very uncertain. However, recent efforts on the analysis of up to date combined astrophysical and nuclear observations have allowed to constrain the value of these quantities with reasonable uncertainity above nuclear saturation [25][26][27][28][29].…”