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The concept of symmetry under various transformations of quantities describing basic natural phenomena is one of the fundamental principles in the mathematical formulation of physical laws. Starting with Noether's theorems, we highlight some well–known examples of global symmetries and symmetry breaking on the particle level, such as the separation of strong and electroweak interactions and the Higgs mechanism, which gives mass to leptons and quarks. The relation between symmetry energy and charge symmetry breaking at both the nuclear level (under the interchange of protons and neutrons) and the particle level (under the interchange of u and d quarks) forms the main subject of this work. We trace the concept of symmetry energy from its introduction in the simple semi-empirical mass formula and liquid drop models to the most sophisticated non-relativistic, relativistic, and ab initio models. Methods used to extract symmetry energy attributes, utilizing the most significant combined terrestrial and astrophysical data and theoretical predictions, are reviewed. This includes properties of finite nuclei, heavy-ion collisions, neutron stars, gravitational waves, and parity–violating electron scattering experiments such as CREX and PREX, for which selected examples are provided. Finally, future approaches to investigation of the symmetry energy and its properties are discussed. [ABSTRACT FROM AUTHOR]

In the present work, we investigate the bulk properties of nuclear matter and neutron stars with the newly proposed relativistic interaction NL-RS which provides an opportunity to readjust the coupling constants keeping in view the properties of finite nuclei, nuclear matter, PREX-II results for neutron skin thickness in 208Pb and astrophysical observations. The NL-RS model interaction has been proposed by fitting the ground state properties (binding energies and charge radii) of finite nuclei, bulk nuclear matter properties, and PREX-II results for neutron skin thickness of 208Pb. The relativistic interaction has been generated by including nonlinear self-interactions of σ and ω μ -mesons and mixed interactions of ω μ , and ρ μ -meson up to the quartic order. The proposed interaction harmonizes with the finite nuclei, bulk nuclear matter, and neutron star properties. A covariance analysis is performed to assess the statistical uncertainties on the model parameters and nuclear observables of interest along with correlations amongst them. The equation of state (EoS) composed of nucleons and leptons in β -equilibrium is computed with the proposed parameter set and used to study the neutron star structure. The maximum mass of the neutron star by employing the EoS computed with the NL-RS parameter set is 2.04 ± 0.03 M ⊙ and the radius of a canonical mass neutron star (R 1.4) comes out to be equal to 13.06 ± 0.16 Km. The value of dimensionless tidal deformability, for canonical mass, is 602.23 ± 33.13 which satisfies the constraints of waveform models analysis of GW170817 within 90% confidence level. [ABSTRACT FROM AUTHOR]

In the present work, we constrain the equations of the state of asymmetric dense matter in consideration of the heaviest observed neutron star mass M max = 2.35 ± 0.17 M ⊙ for the black widow pulsar PSR J0952-0607, finite and bulk nuclear properties. We propose four interactions for the relativistic mean field model which include different combinations of non-linear, self, and cross-couplings among isoscalar–scalar σ , isoscalar–vector ω , isovector–vector ρ and isovector–scalar meson δ meson fields up to the quartic order. These interactions harmonize with the finite nuclei and bulk nuclear matter properties. It is observed that interactions obtained with the inclusion of δ meson coupling with nucleons have a significant effect on the slope of symmetry energy (L), radius (R 1.4 ) , and dimensionless tidal deformability (Λ 1.4) corresponding to a canonical mass neutron star. The radius of 2.08 M ⊙ neutron star mass is predicted to be in the range R 2.08 = 12.98–13.34 km which also satisfies the NICER observations Miller et al. (Astrophys. J. Lett. 918, L28 (2021). [ABSTRACT FROM AUTHOR]

The foundation and applications of the Barcelona Catania Paris Madrid (BCPM) energy density functional are briefly reviewed. BCPM uses a paradigm more rooted on density functional theory and fits most of its parameters to sophisticated microscopic nuclear matter calculations. Finite nuclei are accounted for by introducing a direct finite range surface term, spin orbit potential, Coulomb interaction and pairing. Applications of this functional to the calculation of finite nuclei properties are presented as well as applications to the description of neutron star physics. The large number of applications discussed are possible because of the local character of the functional that simplifies enormously calculations in finite nuclei. [ABSTRACT FROM AUTHOR]

The elasticity of neutron star crust is important for adequate interpretation of observations. To describe elastic properties one should rely on theoretical models. The most widely used is Coulomb crystal model (system of point-like charges on neutralizing uniform background), in some works it is corrected for electron screening. These models neglect finite size of nuclei. This approximation is well justified except for the innermost crustal layers, where nuclei size becomes comparable with the inter-nuclear spacing. Still, even in those dense layers it seems reasonable to apply the Coulomb crystal result, if one assumes that nuclei are spherically symmetric: Coulomb interaction between them should be the same as interaction between point-like charges. This argument is indeed correct; however, as we point here, shear of crustal lattice generates (microscopic) quadrupole electrostatic potential in a vicinity of lattice cites, which induces deformation on the nuclei. We analyse this problem analytically within compressible liquid drop model. In particular, for ground state crust composition the effective shear modulus is reduced for a factor of |$1-u^{5/3}/(2+3\, u-4\, u^{1/3})$|⁠ , where u is the ratio of the nuclei volume to the volume of the cell. This result is universal, i.e. it does not depend on the applied nucleon interaction model within applied approach. For the innermost layers of inner crust u ∼ 0.2 leading to reduction of the shear modulus by |$\sim 25{{\ \rm per\ cent}}$|⁠ , which can be important for correct interpretation of quasi-periodic oscillations in the tails of magnetar flares. [ABSTRACT FROM AUTHOR]

We obtain posterior distribution of equations of state (EOSs) across a broad range of density by imposing explicitly the constraints from precisely measured fundamental properties of finite nuclei, in combination with the experimental data from heavy-ion collisions and the astrophysical observations of radius, tidal deformability and minimum-maximum mass of neutron stars. The acquired EOSs exhibit a distinct global behavior compared to those usually obtained by imposing the finite nuclei constraints implicitly through empirical values of selected key parameters describing symmetric nuclear matter and symmetry energy in the vicinity of the saturation density. The explicit treatment of finite nuclei constraints yields softer EOSs at low densities which eventually become stiffer to meet the maximum mass criteria. The Kullback-Leibler divergence has been used to perform a quantitative comparison of the distributions of neutron star properties resulting from the EOSs obtained from implicit and explicit finite nuclei constraints. [ABSTRACT FROM AUTHOR]

Nuclear saturation is a crucial feature in nuclear physics that plays a fundamental role in understanding various nuclear phenomena, ranging from properties of finite nuclei to those of neutron stars. However, a proper description of nuclear saturation is highly nontrivial in modern nonrelativistic ab initio studies because of the elusive three-body forces. In this letter, we calculate the equation of state for nuclear matter in the relativistic Brueckner-Hartree-Fock (RBHF) framework with the leading order covariant chiral nuclear force. We show that a simultaneous description of the nucleon-nucleon scattering data and the saturation of the symmetric nuclear matter can be achieved. In this regard, the relativistic effects nicely explain the saturation of nuclear matter. As a result, the present study based on the covariant chiral nuclear force shows that in the RBHF framework, one can achieve saturation with a leading order covariant chiral nuclear force with only two-body forces, in contrast to the vast majorities of studies in the non-relativistic framework, where the next-to-next-to-leading order two-body and three-body chiral forces are needed. This study sets the foundation for studying nuclear saturation with the covariant chiral force in the RBHF framework, which allows for a systematic understanding of one of the key features of nuclear physics more microscopically. [ABSTRACT FROM AUTHOR]

The secondary component of the GW190814 event left us with a question, "whether it is a supermassive neutron star or lightest black-hole?" Recently, Fattoyev et al. obtained an energy density functional (EDF) named as BigApple, which reproduces the mass of the neutron star is 2.60 M ⊙ which is well consistent with GW190814 data. This study explores the properties of finite nuclei, nuclear matter and neutron stars by using the BigApple EDF along with four well-known relativistic mean-field forces, namely NL3, G3, IOPB-I and FSUGarnet. The finite nuclei properties like binding energy per particle, skin thickness, charge radius, single-particle energy, and two-neutron separation energy are well predicted by the BigApple for a series of nuclei. The calculated nuclear matter quantities, such as incompressibility, symmetry energy and slope parameters at saturation density, are consistent with the empirical or experimental values where ever available. The predicted canonical tidal deformability by the BigApple parameter set is well-matched with the GW190814 data. Also, the dimensionless moment of inertia lies in the range given by the analysis of PSR J0737-3039A. [ABSTRACT FROM AUTHOR]

A unified description of finite nuclei and equation of state of neutron stars presents both a major challenge and also opportunities for understanding nuclear interactions. Inspired by the Lee–Huang–Yang formula of hard-sphere gases, we develop effective nuclear interactions with an additional high-order density dependent term. While the original Skyrme force SLy4 is widely used in studies of neutron stars, there are not satisfactory global descriptions of finite nuclei. The refitted SLy4' force can improve descriptions of finite nuclei but slightly reduces the radius of neutron star of 1.4M⊙ with M⊙ being the solar mass. We find that the extended SLy4 force with a higher-order density dependence can properly describe properties of both finite nuclei and GW170817 binary neutron stars, including the mass-radius relation and the tidal deformability. This demonstrates the essential role of high-order density dependence at ultrahigh densities. Our work provides a unified and predictive model for neutron stars, as well as new insights for the future development of effective interactions. [ABSTRACT FROM AUTHOR]

When hadron-quark continuity is formulated in terms of a topology change at a density higher than twice the nuclear matter density (n 0) , the core of massive compact stars can be described in terms of quasiparticles of fractional baryon charges, behaving neither like pure baryons nor like deconfined quarks. Hidden symmetries, both local gauge and pseudo-conformal (or broken scale), emerge and give rise both to the long-standing "effective g A ∗ ≈ 1 " in nuclear Gamow–Teller (GT) transitions at ≲ n 0 and to the pseudo-conformal sound velocity v pcs 2 / c 2 ≈ 1 / 3 at ≳ 3 n 0 . It is suggested that what has been referred to, since a long time, as "quenched g A " in light nuclei reflects what leads to the dilaton-limit g A DL = 1 at near the (putative) infrared fixed point of scale invariance. These properties are confronted with the recent observations in GT transitions and in astrophysical observations. [ABSTRACT FROM AUTHOR]

The nuclear matter parameters define the nuclear equation of state (EoS), they appear as coefficients of expansion around the saturation density of symmetric and asymmetric nuclear matter. We review their correlations with several properties of finite nuclei and of neutron stars within mean-field frameworks. The lower order nuclear matter parameters such as the binding energy per nucleon, incompressibility and the symmetry energy coefficients are found to be constrained in narrow limits through their strong ties with selective properties of finite nuclei. From the correlations of nuclear matter parameters with neutron star observables, we further review how precision knowledge of the radii and tidal deformability of neutron stars in the mass range 1 - 2 M ⊙ may help cast them in narrower bounds. The higher order parameters such as the density slope and the curvature of the symmetry energy or the skewness of the symmetric nuclear matter EoS are, however, plagued with larger uncertainty. From inter-correlation of these higher order nuclear matter parameters with lower order ones, we explore how they can be brought to more harmonious bounds. [ABSTRACT FROM AUTHOR]

The study of the finite asymmetric nucleonic matter (ASM) in the periodic boxes (PBs) could play a significant role in the investigation of the finite nuclei as well as the crust of neutron stars. So, in the present contribution, the lowest order constrained variational (LOCV) method is applied to finite ASM in PBs (PBLOCV). In the PBLOCV ASM computations, different sets of finite nucleonic systems are considered, at various proton to neutron ratios (β ), using the Bethe and the central part of the AV ′ 8 potentials. The asymmetric effects are imposed in the statistical correlation functions, in which their PB versions are anisotropic. It is shown that the mentioned anisotropic behavior is the origin of the anisotropy of the PBLOCV ASM nucleon–nucleon distribution functions. As expected, it is found that, for a large number of nucleons and mesh segments, the PBLOCV ASM energies tend to those of LOCV. In other words, for a large PB, the PBLOCV smallness parameters reasonably agree with those of LOCV. The finite size effects (FSEs), which can be employed in quantum Monet Carlo calculations, are illustrated for PBLOCV ASM energies, especially for small periodic boxes, at high β values. It is demonstrated that considering 420 (504) nucleons at β = 0.034 (0.474) , the corresponding PBLOCV energy is notably consistent with those of 1030 nucleons and LOCV. Meanwhile, the PBLOCV ASM data for 14 (16) nucleons at β = 0.000 (0.143) lie far from those of LOCV, for which the FSEs are remarkably evident. [ABSTRACT FROM AUTHOR]

After the first detection of gravitational waves from the merger of a neutron star binary GW170817 which allowed the first measurement of tidal deformability of neutron stars, investigations of the neutron star equations of state that determine the inner structure of neutron stars have increased dramatically. In addition, electromagnetic wave observations at various wave lengths from the same system (GRB170817A and AT 2017gfo) proved the possibility that nuclear and hadronic physics can be studied extensively from neutron star observations. On the other hand, heavy ion collision experiment facilities, including RAON (Rare isotope Accelerator complex for ON-line experiments) which is being built in Korea, are expected to provide excellent environments for the study of dense matter physics. In this review, I summarize recent research activities in Korea in the field of astro-hadron physics focusing on the structure of finite nuclei, rare isotope collisions, and dense stellar matter in neutron stars. Structures of finite nuclei can give constraints to the nuclear matter equations of state near nuclear saturation density (ρ0), rare isotope collisions can give constrains up to 2ρ0, and neutron star can give constraints up to several times nuclear saturation density. [ABSTRACT FROM AUTHOR]

We present predictions for neutron star tidal deformabilities obtained from a Bayesian analysis of the nuclear equation of state, assuming a minimal model at high-density that neglects the possibility of phase transitions. The Bayesian posterior probability distribution is constructed from priors obtained from microscopic many-body theory based on realistic two- and three-body nuclear forces, while the likelihood functions incorporate empirical information about the equation of state from nuclear experiments. The neutron star crust equation of state is constructed from the liquid drop model, and the core-crust transition density is found by comparing the energy per baryon in inhomogeneous matter and uniform nuclear matter. From the cold β -equilibrated neutron star equation of state, we then compute neutron star tidal deformabilities as well as the mass-radius relationship. Finally, we investigate correlations between the neutron star tidal deformability and properties of finite nuclei. [ABSTRACT FROM AUTHOR]

In the present work, we investigate the bulk properties of nuclear matter and neutron stars with the newly proposed relativistic parametrizations HPUA, HPUB and HPUC which provides an opportunity to readjust the coupling parameters keeping in view the properties of finite nuclei, nuclear matter and astrophysical constraints. The HPUA, HPUB and HPUC are proposed by fitting both PREX-II + CREX results simultaneously, PREX-II and CREX results for neutron skin thickness of 208Pb and 48Ca respectively to assess their implications. The relativistic parameterizations have been generated by including non linear self-interactions of σ and ω - mesons and mixed interactions of ω , and ρ -meson up to the quartic order. The new equations of state (EoSs) composed of nucleons and leptons in β - equilibrium are constructed with the newly proposed parameter sets. The maximum mass of the neutron star by employing the EoSs computed with the HPU's parameter sets lies in the range 2.02 ± 0.03 M⊙ - 2.04 ± 0.03 M⊙ and the radius of canonical neutron star (R 1.4) comes out to be equal to 12.89 ± 0.08 Km - 13.27 ± 0.30 Km (including BPS crust). The value of dimensionless tidal deformability, for canonical mass, is 590.83 ± 22.58 - 631.52 ± 78.13 which satisfies the constraints of waveform models analysis of GW170817. A covariance analysis is also performed to calculate the statistical uncertainties in the model parameters and nuclear matter observables along with their correlations. [ABSTRACT FROM AUTHOR]

The D1 family of parametrizations of the Gogny interaction commonly suffers from a rather soft neutron matter equation of state that leads to maximal masses of neutron stars well below the observational value of two solar masses. We propose a reparametrization scheme that preserves the good properties of the Gogny force but allows one to tune the density dependence of the symmetry energy, which, in turn, modifies the predictions for the maximum stellar mass. The scheme works well for D1M, and leads to a new parameter set, dubbed D1M ⁎ . In the neutron-star domain, D1M ⁎ predicts a maximal mass of two solar masses and global properties of the star in harmony with those obtained with the SLy4 Skyrme interaction. By means of a set of selected calculations in finite nuclei, we check that D1M ⁎ performs comparably well to D1M in several aspects of nuclear structure in nuclei. [ABSTRACT FROM AUTHOR]

Background: Theoretical approaches based on density functional theory provide the only tractable method to incorporate the wide range of densities and isospin asymmetries required to describe finite nuclei, infinite nuclear matter, and neutron stars. Purpose: A relativistic energy density functional (EDF) is developed to address the complexity of such diverse nuclear systems. Moreover, a statistical perspective is adopted to describe the information content of various physical observables. Methods: We implement the model optimization by minimizing a suitably constructed Χ² objective function using various properties of finite nuclei and neutron stars. The minimization is then supplemented by a covariance analysis that includes both uncertainty estimates and correlation coefficients. Results: A new model, "FSUGold2," is created that can well reproduce the ground-state properties of finite nuclei, their monopole response, and that accounts for the maximum neutron-star mass observed up to date. In particular, the model predicts both a stiff symmetry energy and a soft equation of state for symmetric nuclear matter, suggesting a fairly large neutron-skin thickness in Pb208 and a moderate value of the nuclear incompressibility. Conclusions: We conclude that without any meaningful constraint on the isovector sector, relativistic EDFs will continue to predict significantly large neutron skins. However, the calibration scheme adopted here is flexible enough to create models with different assumptions on various observables. Such a scheme--properly supplemented by a covariance analysis--provides a powerful tool to identify the critical measurements required to place meaningful constraints on theoretical models. [ABSTRACT FROM AUTHOR]

A method is introduced that establishes relations between properties of collective excitations in finite nuclei and the phase transition density n, and pressure Pt at the inner edge separating the liquid core and the solid crust of a neutron star. A theoretical framework that includes the thermodynamic method, relativistic nuclear energy density functionals, and the quasiparticle random-phase approximation is employed in a self-consistent calculation of (nt, Pt) and collective excitations in nuclei. Covariance analysis shows that properties of charge-exchange dipole transitions, isovector giant dipole and quadrupole resonances, and pygmy dipole transitions are correlated with the core-crust transition density and pressure. A set of relativistic nuclear energy density functionals, characterized by systematic variation of the density dependence of the symmetry energy of nuclear matter, is used to constrain possible values for (nt, Pt). By comparing the calculated excitation energies of giant resonances, energy-weighted pygmy dipole strength, and dipole polarizability with available data, we obtain the weighted average values: nt = 0.0955 ± 0.0007 fm-3 and Pt = 0.59 ± 0.05 MeV fm-3. This approach crucially depends on experimental results for collective excitations in nuclei and, therefore, accurate measurements are necessary to further constrain the structure of the crust of neutron stars. [ABSTRACT FROM AUTHOR]

The Lead Radius Experiment has provided the first model-independent evidence in favor of a neutron-rich skin in 208Pb. Although the error bars are large, the reported large central value of 0.33 fm is particularly intriguing. To test whether such a thick neutron skin in 208Pb is already incompatible with laboratory experiments or astrophysical observations, we employ relativistic models with neutron-skin thickness in 208Pb ranging from 0.16 to 0.33 fm to compute ground-state properties of finite nuclei, their collective monopole and dipole response, and mass-versus-radius relations for neutron stars. No compelling reason was found to rule out models with large neutron skins in 208Pb from the set of observables considered in this Letter. [ABSTRACT FROM AUTHOR]

Abstract: We have optimized the parameters of extended relativistic mean-field model using a selected set of global observables which includes binding energies and charge radii for nuclei along several isotopic and isotonic chains and the iso-scalar giant monopole resonance energies for the 90Zr and 208Pb nuclei. The model parameters are further constrained by the available informations on the energy per neutron for the dilute neutron matter and bounds on the equations of state of the symmetric and asymmetric nuclear matter at supra-nuclear densities. Two new parameter sets BSP and IUFSU* are obtained, later one being the variant of recently proposed IUFSU parameter set. The BSP parametrization uses the contributions from the quartic order cross-coupling between ω and σ mesons to model the high density behaviour of the equation of state instead of the ω meson self-coupling as in the case of IUFSU* or IUFSU. Our parameter sets yield appreciable improvements in the binding energy systematics and the equation of state for the dilute neutron matter. The importance of the quartic order ω–σ cross coupling term of the extended RMF model, as often ignored, is realized. [Copyright &y& Elsevier]

We investigated the superfluid properties of the inner crust of neutron stars, solving the Hartree-Fock-Bogoliubov equations in spherical Wigner-Seitz cells. Using realistic two-body interactions in the pairing channel, we studied in detail the Cooper-pair and the pairing-field spatial properties, together with the effect of the proton clusters on the neutron pairing gap. Calculations with effective pairing interactions are also presented, showing significant discrepancies with the results obtained with realistic pairing forces. At variance with recent studies on finite nuclei, the neutron coherence length is found to depend on the strength of the pairing interaction, even inside the nucleus. We also show that the spherical Wigner-Seitz approximation breaks down in the innermost regions of the inner crust, already at baryonic densities ρb ≥ 8 × 10+13 g/cm3. [ABSTRACT FROM AUTHOR]

Abstract: Within a relativistic mean-field model with nonlinear isoscalar–isovector coupling, we explore the possibility of constraining the density dependence of nuclear symmetry energy from a systematic study of the neutron skin thickness of finite nuclei and neutron star properties. We find the present skin data supports a rather stiff symmetry energy at subsaturation densities that corresponds to a soft symmetry energy at supranormal densities. Correlation between the skin of 208Pb and the neutron star masses and radii with kaon condensation has been studied. We find that 208Pb skin estimate suggest star radii that reveals considerable model dependence. Thus precise measurements of neutron star radii in conjunction with skin thickness of heavy nuclei could provide significant constraint on the density dependence of symmetry energy. [Copyright &y& Elsevier]

Abstract: Self-consistent mean field models are a powerful tool in the investigation of nuclear structure and low-energy dynamics. They are based on effective energy-density functionals, often formulated in terms of effective density-dependent nucleon–nucleon interactions. The free parameters of the functional are adjusted to empirical data. A proper choice of these parameters requires a comprehensive set of constraints covering experimental data on finite nuclei, concerning static as well as dynamical properties, empirical characteristics of nuclear matter, and observational information on nucleosynthesis, neutron stars and supernovae. This work aims at a comprehensive survey of the performance of one of the most successful non-relativistic self-consistent method, the Skyrme–Hartree–Fock model (SHF), with respect to these constraints. A full description of the Skyrme functional is given and its relation to other effective interactions is discussed. The validity of the application of SHF far from stability and in dense environments beyond the nuclear saturation density is critically assessed. The use of SHF in models extended beyond the mean field approximation by including some correlations, is discussed. Finally, future prospects for further development of SHF towards a more consistent application of the existing and promising newly developing constraints are outlined. [Copyright &y& Elsevier]

Role of the isospin asymmetry in nuclei and neutron stars, with an emphasis on the density dependence of the nuclear symmetry energy, is discussed. The symmetry energy is obtained using the isoscalar as well as isovector components of the density dependent M3Y effective interaction. The constants of density dependence of the effective interaction are obtained by reproducing the saturation energy per nucleon and the saturation density of spin and isospin symmetric cold infinite nuclear matter. Implications for the density dependence of the symmetry energy in case of a neutron star are discussed, and also possible constraints on the density dependence obtained from finite nuclei are compared. [ABSTRACT FROM AUTHOR]

The effective Gogny interactions of the D1 family were established by D. Gogny more than forty years ago with the aim to describe simultaneously the mean field and the pairing field corresponding to the nuclear interaction. The most popular Gogny parametrizations, namely D1S, D1N and D1M, describe accurately the ground-state properties of spherical and deformed finite nuclei all across the mass table obtained with Hartree–Fock–Bogoliubov (HFB) calculations. However, these forces produce a rather soft equation of state (EoS) in neutron matter, which leads to predict maximum masses of neutron stars well below the observed value of two solar masses. To remove this limitation, we built new Gogny parametrizations by modifying the density dependence of the symmetry energy predicted by the force in such a way that they can be applied to the neutron star domain and can also reproduce the properties of finite nuclei as good as their predecessors. These new parametrizations allow us to obtain stiffer EoS's based on the Gogny interactions, which predict maximum masses of neutron stars around two solar masses. Moreover, other global properties of the star, such as the moment of inertia and the tidal deformability, are in harmony with those obtained with other well tested EoSs based on the SLy4 Skyrme force or the Barcelona–Catania–Paris–Madrid (BCPM) energy density functional. Properties of the core-crust transition predicted by these Gogny EoSs are also analyzed. Using these new Gogny forces, the EoS in the inner crust is obtained with the Wigner–Seitz approximation in the Variational Wigner–Kirkwood approach along with the Strutinsky integral method, which allows one to estimate in a perturbative way the proton shell and pairing corrections. For the outer crust, the EoS is determined basically by the nuclear masses, which are taken from the experiments, wherever they are available, or by HFB calculations performed with these new forces if the experimental masses are not known. [ABSTRACT FROM AUTHOR]

Nucleon-nucleon short-range correlations (SRCs) are inevitable consequences of realistic nucleon-nucleon interactions. The corresponding SRC pairs, characterized by high relative momenta, have been verified experimentally to be important in finite nuclei. In this work, we study the impacts of nucleon-nucleon SRCs on the physical properties of neutron stars. Considering the small center-of-mass momenta of SRC pairs, new nucleon momentum distributions with high-momentum tails (HMTs) are proposed by extrapolating well-established experimental results of SRCs in finite nuclei to neutron star matter. HMTs with different shapes are adopted to estimate theoretical uncertainties. It is found that nucleon-nucleon SRCs generally stiffen the equation of state of neutron star matter and increase the maximum mass of neutron stars. [ABSTRACT FROM AUTHOR]

The decay of 28Si⁎ compound system formed by 12C+16O reaction is analyzed at stellar energies span E c. m. = 4 - 5 MeV. The conventional SIII Skyrme force is used in conjunction with generalized GSkI and extended eMSL07 Skyrme forces having extended density-dependent terms, that can be potentially useful for the study of finite nuclei and the neutron stars. The dynamical cluster-decay model (DCM) is used to examine the emission of n, p, and α particles in the decay of 28Si⁎ nucleus along with other competing decay channels. The theoretical analysis advocates the emergence of 6Li, 10B, and 14N fragments in the decay of 28Si⁎ nucleus, independent of the choice of Skyrme interactions and the angular momentum effects. The fragile nature of 6Li nucleus may not allow it to survive the stellar conditions and hence the breakup and /or radiative capture processes may appear in. The breakup of L 6 i is addressed in terms of Kinetic energy (K.E) value of A=6 fragment while the possibility of capture reaction is predicted in terms of positive Q values of radiative capture reactions 6Li(n, γ)7Li, 6Li(p, γ)7Be, and 6Li(α , γ)10B. It has been observed that the structure of fragmentation potential and preformation probability is independent of the choice of Skyrme forces, but their magnitude gets significantly influenced for use of different Skyrme forces. The conventional SIII force could not reproduce the cross sections while eMSL07 and GSkI Skyrme forces give nice agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Mutual entrainment effects in cold neutron-proton mixtures are studied in the framework of the self-consistent nuclear energy-density functional theory. Exact expressions for the mass currents, valid for both homogeneous and inhomogeneous systems, are directly derived from the time-dependent Hartree-Fock equations with no further approximation. The equivalence with the Fermi-liquid expression is also demonstrated. Focusing on neutron-star cores, a convenient and simple analytical formulation of the entrainment matrix in terms of the isovector effective mass is found, thus allowing one to relate entrainment phenomena in neutron stars to isovector giant dipole resonances in finite nuclei. Results obtained with different functionals are presented. These include the Brussels-Montreal functionals, for which unified equations of state of neutron stars have been recently calculated. [ABSTRACT FROM AUTHOR]

We analyze the effects of including Δ(1232) isobars in an equation of state (EoS) for cold, β-stable neutron star (NS) matter, employing relativistic nuclear mean field theory. The selected EoS reproduces the properties of nuclear matter and finite nuclei and, in the astrophysical context, allows for the presence of hyperons in NSs having masses larger than 2 M⊙. We find that the composition and structure of NSs is critically influenced by the addition of the Δ isobars, which allows us to constrain their interaction with the meson fields, taking into account astrophysical information. Imposing that the EoS is stable and ensures the existence of 2 M⊙ NSs, as well as requiring agreement with data of Δ excitation in nuclei, we find that, in the absence of other mechanisms stiffening the EoS at high densities, the interaction of the Δ isobars with the sigma and omega meson fields must be at least 10% stronger than those of the nucleons. Moreover, the NS moment of inertia turns out to be sensitive to the presence of Δ isobars, whereas the inclusion of Δ isobars in the EoS allows for smaller stellar radii and for a lower value of the tidal deformability, consistent with the analysis of the GW170817 merger event. [ABSTRACT FROM AUTHOR]

We investigate neutron star moments of inertia from Bayesian posterior probability distributions of the nuclear equation of state that incorporate information from microscopic many-body theory and empirical data of finite nuclei. We focus on PSR J0737-3039A and predict that for this 1.338M⊙ neutron star the moment of inertia lies in the range 1.04×1045gcm²

Nuclear matter and finite nuclei exhibit the property of superfluidity by forming Cooper pairs. We review the microscopic theories and methods that are being employed to understand the basic properties of superfluid nuclear systems, with emphasis on the spatially extended matter encountered in neutron stars, supernova envelopes, and nuclear collisions. Our survey of quantum many-body methods includes techniques that employ Green functions, correlated basis functions, and Monte Carlo sampling of quantum states. With respect to empirical realizations of nucleonic and hadronic superfluids, this review is focused on progress that has been made toward quantitative understanding of their properties at the level of microscopic theories of pairing, with emphasis on the condensates that exist under conditions prevailing in neutron-star interiors. These include singlet S-wave pairing of neutrons in the inner crust, and, in the quantum fluid interior, singlet-S proton pairing and triplet coupled P-F-wave neutron pairing. Additionally, calculations of weak-interaction rates in neutron-star superfluids within the Green function formalism are examined in detail. We close with a discussion of quantum vortex states in nuclear systems and their dynamics in neutron-star superfluid interiors. [ABSTRACT FROM AUTHOR]

Background: In the framework of the newly developed generalized energy density functional (EDF) called KIDS, the nuclear equation of state (EoS) is expressed as an expansion in powers of the Fermi momentum or the cubic root of the density (ρ1/3). Although an optimal number of converging terms was obtained in specific cases of fits to empirical data and pseudodata, the degree of convergence remains to be examined not only for homogeneous matter but also for finite nuclei. Furthermore, even for homogeneous matter, the convergence should be investigated with widely adopted various EoS properties at saturation. Purpose: The first goal is to validate the minimal and optimal number of EoS parameters required for the description of homogeneous nuclear matter over a wide range of densities relevant for astrophysical applications. The major goal is to examine the validity of the adopted expansion scheme for an accurate description of finite nuclei. Method: We vary the values of the high-order density derivatives of the nuclear EoS, such as the skewness of the energy of symmetric nuclear matter and the kurtosis of the symmetry energy, at saturation and examine the relative importance of each term in ρ1/3 expansion for homogeneous matter. For given sets of EoS parameters determined in this way, we define equivalent Skyrme-type functionals and examine the convergence in the description of finite nuclei focusing on the masses and charge radii of closed-shell nuclei. Results: The EoS of symmetric nuclear matter is found to be efficiently parameterized with only three parameters and the symmetry energy (or the energy of pure neutron matter) with four parameters when the EoS is expanded in the power series of the Fermi momentum. Higher-order EoS parameters do not produce any improvement, in practice, in the description of nuclear ground-state energies and charge radii, which means that they cannot be constrained by bulk properties of nuclei. Conclusions: The minimal nuclear EDF obtained in the present work is found to reasonably describe the properties of closed-shell nuclei and the mass-radius relation of neutron stars. Attempts at refining the nuclear EDF beyond the minimal formula must focus on parameters which are not active (or strongly active) in unpolarized homogeneous matter, for example, effective tensor terms and time-odd terms. [ABSTRACT FROM AUTHOR]

The first detection of gravitational waves from the binary neutron star merger event GW170817 has started to provide important new constraints on the nuclear equation of state at high density. The tidal deformability bound of GW170817 combined with the observed two solar mass neutron star poses a serious challenge to theoretical formulations of realistic equations of state. We analyze a fully comprehensive set of relativistic nuclear mean-field theories by confronting them with the observational bounds and the measured neutron-skin thickness. We find that only a few models can withstand these bounds which predict a stiff overall equation of state but with a soft neutron-proton symmetry energy. Two possible indications are proposed: Circumstantial evidence of hadron-quark phase transition inside the star and new parametrizations that are consistent with ground-state properties of finite nuclei and observational bounds. Based on extensive analysis of these sets, an upper limit on the radius of a 1.4M⊙ neutron star of R1.4≲12.9 km is deduced. [ABSTRACT FROM AUTHOR]

The agreement of the nuclear equation of state (EOS) deduced from the GW170817-based tidal deformability with the one obtained from empirical data on microscopic nuclei is examined. It is found that suitably chosen experimental data on isoscalar and isovector modes of nuclear excitations together with the observed maximum neutron star mass constrain the EOS which displays a very good congruence with the GW170817 inspired one. The giant resonances in nuclei are found to be instrumental in limiting the tidal deformability parameter and the radius of a neutron star in somewhat narrower bounds. At the 1σ level, the values of the canonical tidal deformability Λ1.4 and the neutron star radius R1.4 come out to be 267±144 and 11.6±1.0 km, respectively. [ABSTRACT FROM AUTHOR]

Background: The first direct detection of a binary neutron star merger by the LIGO Scientific Collaboration and the Virgo Collaboration (LIGO-Virgo) [Phys. Rev. Lett. 119, 161101 (2017)] has opened the brand new era of multimessenger astronomy. This historic detection has been instrumental in providing initial constraints on the tidal polarizability (or deformability) of neutron stars. In turn, the tidal polarizability--an observable highly sensitive to stellar compactness--has been used to impose limits on stellar radii and ultimately on the underlying equation of state (EOS). Purpose: Besides its strong dependence on the stellar compactness, the tidal polarizability is also sensitive to the second tidal Love number k2. It is the main purpose of this paper to perform a detailed study of k2 which, for a given compactness parameter, encodes the entire sensitivity of the tidal polarizability to the underlying equation of state. In particular, we examine the important role that the crustal component of the EOS plays in the determination of k2. Methods: A set of realistic models of the equation of state that yield an accurate description of the properties of finite nuclei support neutron stars of two solar masses and provide a Lorentz covariant extrapolation to dense matter are used to solve both the Tolman-Oppenheimer-Volkoff and the differential equations for the induced quadrupole gravitational field from which k2 is extracted. Results: Given that the tidal polarizability scales as the fifth power of the compactness parameter, a universal relation exists among the tidal polarizability and the compactness parameter that is highly insensitive to the underlying equation of state. Thus, besides an extraction of the tidal polarizabilities, a measurement of the individual stellar masses is also required to impact the mass-radius relation. However, we observe a strong sensitivity of the second Love number to the underlying equation of state--particularly to the contribution from the inner crust. Conclusions: Although by itself the tidal polarizability cannot contribute to the determination of the mass-radius relation, future detections of binary neutron star mergers by the LIGO-Virgo Collaborations during the third observing run and beyond are poised to provide significant constraints on both the tidal polarizabilities and the masses of the individual stars, and thus ultimately on the mass-radius relation. Yet, subleading corrections to the tidal polarizability are encoded in the second Love number k2, which displays a large sensitivity to the entire--crust-plus-core--equation of state. [ABSTRACT FROM AUTHOR]

Neutron star matter is investigated in a hadronic chiral model approach using the lowest flavor-SU(3) multiplets for baryons and mesons. The parameters are determined to yield consistent results for saturated nuclear matter as well as for finite nuclei. The influence of baryonic resonances is discussed. The global properties of a neutron star such as its mass and radius are determined. Proto-neutron star properties are studied by taking into account trapped neutrinos, temperature and entropy effects. [ABSTRACT FROM AUTHOR]