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We investigate the thermodynamic instabilities of asymmetric nuclear matter (ANM) from the mechanical (isoscalar) and chemical (isovector) points of view in the framework of a statistical model that complies with the Thomas–Fermi approximation, employing the Myers and Swiatecki (MS) interactions. Our findings show that the spinodal instabilities drive the dense system towards lower asymmetry parameters, while neither pure mechanical nor pure chemical natures are predicted. Meanwhile, by paying attention to the behavior of the nuclear symmetry free energy, which plays a significant role in determining the chemical instability, the instability goes predominantly in the mechanical direction. The results of this model are consistent with those from other theoretical predictions. [ABSTRACT FROM AUTHOR]

Abstract An isentropic description of the equation of state (EOS) for β -stable nuclear matter (BSNM) is presented in a semi-classical mean-field model. Within the Thomas–Fermi (TF) approximation, the Landau Fermi-liquid theory (LFT) is used in a self-consistent approach. Accordingly, isentropic thermodynamics of BSNM is investigated for the neutrino-free and neutrino-trapped cases. We find that the EOS for neutrino-trapped matter is stiffer than the one for neutrino-free matter. Our findings can set the stage for profound studies about the structure and composition of proto-neutron stars (PNSs). [ABSTRACT FROM AUTHOR]

The equation of state (EOS) of nuclear matter is investigated in a semi-classical mean-field (MF) approach. Starting from the phase-space NN-interaction of Myers and Swiatecki [ Nucl. Phys. A 601 (1996) 141], the EOS of nuclear matter by the Thomas-Fermi approximation is derived. A self-consistent semi-classical approach is presented by employing the Landau Fermi-Liquid theory (LFT). In our statistical approach, the phase-space occupation number can be expressed in terms of an extended effective mass which is affected by both temperature and nucleonic density. Accordingly, an explicit expression of the nucleonic chemical potential inside the nucleonic occupation number can be obtained. Special attention is also devoted to the density dependence of the nuclear symmetry free energy at different temperatures. The results of this model are compared with other theoretical predictions. [ABSTRACT FROM AUTHOR]

We analyze the thermal effects on the EOS of dense nuclear matter, using a statistical approach where a semi-classical mean-field (MF) model based on the Thomas-Fermi (TF) approximation is introduced. Within this density-functional-based theory, the equation of state (EOS) of hot dense nuclear matter for different compositions of baryonic matter such as symmetric nuclear matter (SNM), pure neutron matter (PNM), and neutrino-free (neutrino-trapped) matter in β -equilibrium is investigated, while the contribution of photons is taken into account for only the β -equilibrated cases. The Landau effective mass, by which the thermal effects on dense matter can be judged, is also extracted from the cold single-particle (SP) potential of neutrons in phase space for both SNM and PNM. We show that the characteristic behavior of the nuclear symmetry free energy (SFE), especially at supra-saturation densities, has a clear relevance to the general influence of the temperature on the EOS. Based on the Γ-law approximation, a simple parametrization for the thermal properties of the EOS is provided by the thermal index Γ t h , while the presence of trapped neutrinos in β -equilibrated matter gives rise to significantly more consistency with the original astrophysical range 1.5 ≤ Γ t h ≤ 2. Our EOSs are then employed in an isentropic scheme to investigate the properties of a hot compact object under the assumption of the conserved baryonic mass, while complying with the current observational constraints on the structure of neutron stars (NSs). Within the present model, we cannot predict the possibility that the lighter component of GW190814 [1] is a massive cold neutron star (NS). [ABSTRACT FROM AUTHOR]

The equation of state (EOS) of hybrid neutron star (HNS) matter is investigated within a model where the phase transition from non-strange baryonic matter to quark matter is described with the help of the Gibbs construction. We use the Myers and Swiatecki (MS) interactions of TF(96) and TF(90) to extract the EOS of β -stable nuclear matter from the Thomas–Fermi (TF) approximation in a semi-classical mean-field (MF) model. The EOS of the deconfined quark phase is obtained from the Nambu–Jona–Lasinio (NJL) model. In studying the EOS of HNS matter, we take into account the two-solar-mass constraint placed by the measurement of the masses of pulsars PSR J1614 − 2230, PSR J0348＋ 0432 and PSR J0740 + 6620. We find that the vector coupling of the NJL model has a strong influence on the formation of the stable HNSs. Our results show that the pure quark phase does not exist in the inner core of HNSs. As the repulsion in the quark matter EOS becomes stronger, the stable configurations of an HNS are formed at lower values of the stellar radius. The quark phase with larger repulsive vector interaction indicates smaller mixed phase region in the inner core of the same-mass HNSs. In addition, the stable HNSs occur at larger radii for the configurations constructed using the stiffer one of the two baryonic EOSs we considered [TF(90)]. • Baryon–quark mixed phase is studied in neutron star matter. • Thomas–Fermi approximation for nucleons and NJL model for quarks are used. • Vector coupling of NJL model plays a key role on the neutron star structure. • Existence of a pure quark phase is excluded in the core of neutron stars. • Mixed phase shrinks in the core of same-mass neutron stars. [ABSTRACT FROM AUTHOR]