Role of isospin physics in supernova matter and neutron stars (original) (raw)
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Journal of Physics: Conference Series, 2013
Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and the equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of neutron stars. In this paper we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at subsaturation density, and the possible strange transition at super-saturation density in the presence of hyperonic degrees of freedom. Concerning the neutron star crust-core phase transition at zero and finite temperature, it will be shown that, as a consequence of the presence of long-range Coulomb interactions, a clusterized phase is expected which is not accessible in the grandcanonical ensemble. A specific quasi-particle model will be introduced and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core also modifies the equation of state. The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.
Probing the metastability of a protoneutron star with hyperons in a core-collapse supernova
Physical Review C, 2014
We investigate the role of hyperons in the dynamical collapse of a non-rotating massive star to a black hole(BH) using one dimensional general relativistic GR1D code. We follow the dynamical formation and evolution of a protoneutron star (PNS) to a black hole using various progenitor models, adopting a hyperonic equation of state (EoS) generated by Shen et. al. We compare the results with those of nuclear EoS by Shen et. al. and understand the role of strange hyperons in the core collapse supernova. We discuss the neutrino signals that may be used as a probe to core collapse. Further, an exotic EoS can support a much lower maximum mass cold neutron star compared to PNS. In this regard, we also study the metastability of PNS in the presence of hyperon in the long-time evolution of the progenitors, relevant to supernova SN1987A. PACS numbers: 26.60.Kp, 26.50.+x, 26.60.-c, 14.20.Jn 1 I. INTRODUCTION
Nuclear liquid-gas phase transition and supernovae evolution
Physical Review C, 2004
It is shown that the large density fluctuations appearing at the onset of the first order nuclear liquid-gas phase transition can play an important role in the supernovae evolution. Due to these fluctuations, the neutrino gas may be trapped inside a thin layer of matter near the proto-neutron star surface. The resulting increase of pressure may induce strong particle ejection a few hundred milliseconds after the bounce of the collapse, contributing to the revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range nucleon-nucleon effective interaction, is employed to estimate the effects of the neutrino trapping due to the strong density fluctuations, and to discuss qualitatively the consequences of the suggested new scenario.
Phase diagram of neutron-rich nuclear matter and its impact on astrophysics
Journal of Physics: Conference Series, 2013
Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of neutron stars. In this paper we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at subsaturation density, and the possible strange transition at super-saturation density in the presence of hyperonic degrees of freedom. Concerning the neutron star crust-core phase transition at zero and finite temperature, it will be shown that, as a consequence of the presence of long-range Coulomb interactions, the equivalence of statistical ensembles is violated and a clusterized phase is expected which is not accessible in the grand-canonical ensemble. A specific quasi-particle model will be introduced to illustrate this anomalous thermodynamics and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core modifies the equation of state.The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach. arXiv:1209.0270v1 [nucl-th] 3 Sep 2012 temperatures between some hundreds of keV and around 80 MeV, and proton fractions between ≈ 0.5 and ≈ 0.1.
Hot Neutron Star Matter and Proto-Neutron Stars
2021
In this chapter, we investigate the structure and composition of hot neutron star matter and proto-neutron stars. Such objects are made of baryonic matter that is several times denser than atomic nuclei and tens of thousands times hotter than the matter in the core of our Sun. The relativistic finite-temperature Green function formalism is used to formulate the expressions that determine the properties of such matter in the framework of the density-dependent mean field approach. Three different sets of nuclear parametrizations are used to solve the many-body equations and to determine the models for the equation of state of ultra-hot and dense stellar matter. The meson-baryon coupling scheme and the role of the ∆(1232) baryon in proto-neutron star matter are investigated in great detail. In addition, using the non-local three-flavor Nambu—Jona-Lasinio model to describe quark matter, the hadron-quark composition of dense baryonic matter at zero temperature is discussed briefly. Gener...
Isospin-dependent clusterization of neutron-star matter
Nuclear Physics A, 2007
Because of the presence of a liquid-gas phase transition in nuclear matter, compactstar matter can present a region of instability against the formation of clusters. We investigate this phase separation in a matter composed of neutrons, protons and electrons, within a Skyrme-Lyon mean-field approach. Matter instability and phase properties are characterized through the study of the free-energy curvature. The effect of β-equilibrium is also analyzed in detail, and we show that the opacity to neutrinos has an influence on the presence of clusterized matter in finite-temperature proto-neutron stars.
Strangeness-driven phase transition in (proto-)neutron star matter
Physical Review C, 2013
The phase diagram of a system constituted of neutrons, protons, Λ-hyperons and electrons is evaluated in the mean-field approximation in the complete three-dimensional space given by the baryon, lepton and strange charge. It is shown that the phase diagram at sub-saturation densities is strongly affected by the electromagnetic interaction, while it is almost independent of the electric charge at supra-saturation density. As a consequence, stellar matter under the condition of strangeness equilibrium is expected to experience a first as well as a second-order strangeness-driven phase transition at high density, while the liquid-gas phase transition is expected to be quenched. An RPA calculation indicates that the presence of this critical point might have sizable implications for the neutrino propagation in core-collapse supernovae. PACS numbers: 26.50.+x, 26.60.-c 21.65.Mn, 64.10.+h, 64.60.Bd,
Warm asymmetric nuclear matter and proto-neutron star structure
Physical Review C, 2004
Asymmetric nuclear matter equation of state at finite temperature is studied in SU(2) chiral sigma model using mean field approximation. The effect of temperature on effective mass, entropy, and binding energy is discussed. Treating the system as one with two conserved charges the liquid-gas phase transition is investigated. We have also discussed the effect of proton fraction on critical temperature with and without ρ-meson contribution. We have extended our work to study the structure of protoneutron star with neutron free charge-neutral matter in beta-equilibrium. We found that the mass and radius of the star decreases as it cools from the entropy per baryon S = 2 to S = 0 and the maximum temperature of the core of the star is about 62 MeV for S = 2.
Physical Review C, 2016
A consistent Hartree-Fock study of the equation of state (EOS) of asymmetric nuclear matter at finite temperature has been performed using realistic choices of the effective, density dependent nucleon-nucleon (NN) interaction, which were successfully used in different nuclear structure and reaction studies. Given the importance of the nuclear symmetry energy in the neutron star formation, EOS's associated with different behaviors of the symmetry energy were used to study hot asymmetric nuclear matter. The slope of the symmetry energy and nucleon effective mass with increasing baryon density was found to affect the thermal properties of nuclear matter significantly. Different density dependent NN interactions were further used to study the EOS of hot protoneutron star (PNS) matter of the npeµν composition in β-equilibrium. The hydrostatic configurations of PNS in terms of the maximal gravitational mass M max and radius, central density, pressure and temperature at the total entropy per baryon S/A = 1, 2 and 4 have been determined in both the neutrino-free and neutrino-trapped scenarios. The obtained results show consistently a strong impact of the symmetry energy and nucleon effective mass on thermal properties and composition of hot PNS matter. M max values obtained for the (neutrino-free) β-stable PNS at S/A = 4 were used to assess time t BH of the collapse of 40 M ⊙ protoneutron progenitor to black hole, based on a correlation between t BH and M max found from the hydrodynamic simulation by Hempel et al..