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We have obtained the constraints on the density dependence of the symmetry energy from neutron-skin thickness data by parity-violating electron scatterings and neutron-star observables using a Bayesian approach, based on the standard Skyrme-Hartree-Fock (SHF) model and its extension as well as the relativistic mean-field (RMF) model. While the neutron-skin thickness data (neutron-star observables) mostly constrain the symmetry energy at subsaturation (suprasaturation) densities, they may more or less constrain the behavior of the symmetry energy at suprasaturation (subsaturation) densities, depending on the energy-density functional form. Besides showing the final posterior density dependence of the symmetry energy, we also compare the slope parameters of the symmetry energy at 0.10 fm−3 as well as the values of the symmetry energy at twice saturation density from three effective nuclear interactions. The present work serves as a comparison study based on relativistic and non-relativistic energy-density functionals, for constraining the nuclear symmetry energy from low to high densities using a Bayesian approach. [ABSTRACT FROM AUTHOR]

It has recently been suggested that differences in the charge radii of mirror nuclei (ΔRchmirr) are strongly correlated with the neutron-skin thickness (Rskin) of neutron-rich nuclei and with the slope of the symmetry energy (L). To test this assumption, we present ab initio calculations of Rskin in 48Ca and 208Pb, ΔRchmirr in 36Ca−36S, 38Ca−38Ar, 41Sc−41Ca, 48Ni−48Ca, 52Ni−52Cr, and 54Ni−54Fe mirror pairs, and L. Employing the recently developed 34 chiral interaction samples, identified by the history matching approach, we conduct rigorous statistical analysis of correlations among ΔRchmirr, Rskin and L, accounting for quantified uncertainties from low-energy constants of chiral interaction, chiral effective field theory truncation and many-body method approximation. The ab initio results reveal an appreciable ΔRchmirr−L correlation in fp-shell mirror pairs. However, contrary to previous studies, the present calculation finds that the studied sd-shell mirror pairs do not exhibit any ΔRchmirr−L correlation.

To improve the constraints of symmetry energy at subsaturation density, measuring and accumulating more neutron skin data for neutron-rich unstable nuclei is naturally required. Aiming to probe the neutron skin of unstable nuclei by using low-intermediate-energy heavy-ion collisions, we develop a new version of an improved quantum molecular dynamics model, in which the neutron skin of the initial nucleus and the mean-field potential in nucleon propagation are consistently treated. Our calculations show that the three observables, such as the cross-sections of the primary projectile-like residues with A > 100 ( σ A > 100 ), the difference of σ A > 100 between 132 Sn + 124 Sn and 124 Sn + 124 Sn systems ( δ σ A > 100 ), and the neutron-to-proton yield ratio ( R (n / p) ) in the transverse direction, could be used to measure the neutron skin of the unstable nuclei and to constrain the slope of the symmetry energy in the future. [ABSTRACT FROM AUTHOR]

Infinite nuclear matter is a suitable laboratory to learn about nuclear forces in many-body systems. In particular, modern theoretical predictions of neutron-rich matter are timely because of recent and planned experiments aimed at constraining the equation of state of isospin-asymmetric matter. For these reasons, we have taken a broad look at the equation of state of neutron-rich matter and the closely related symmetry energy, which is the focal point of this article. Its density dependence is of paramount importance for a number of nuclear and astrophysical systems, ranging from neutron skins to the structure of neutron stars. We review and discuss ab initio predictions in relation to recent empirical constraints. We emphasize and demonstrate that free-space nucleon–nucleon data pose stringent constraints on the density dependence of the neutron matter equation of state, which essentially determines the slope of the symmetry energy at saturation. [ABSTRACT FROM AUTHOR]

It has recently been suggested that differences in the charge radii of mirror nuclei (Δ R ch mirr) are strongly correlated with the neutron-skin thickness (R skin) of neutron-rich nuclei and with the slope of the symmetry energy (L). To test this assumption, we present ab initio calculations of R skin in 48Ca and 208Pb, Δ R ch mirr in 36Ca − 36 S, 38Ca − 38 Ar, 41Sc − 41 Ca, 48Ni − 48 Ca, 52Ni − 52 Cr, and 54Ni − 54 Fe mirror pairs, and L. Employing the recently developed 34 chiral interaction samples, identified by the history matching approach, we conduct rigorous statistical analysis of correlations among Δ R ch mirr , R skin and L , accounting for quantified uncertainties from low-energy constants of chiral interaction, chiral effective field theory truncation and many-body method approximation. The ab initio results reveal an appreciable Δ R ch mirr − L correlation in fp -shell mirror pairs. However, contrary to previous studies, the present calculation finds that the studied sd -shell mirror pairs do not exhibit any Δ R ch mirr − L correlation. [ABSTRACT FROM AUTHOR]

To improve the constraints of symmetry energy at subsaturation density, measuring and accumulating more neutron skin data for neutron-rich unstable nuclei is naturally required. Aiming to probe the neutron skin of unstable nuclei by using low-intermediate-energy heavy-ion collisions, we develop a new version of an improved quantum molecular dynamics model, in which the neutron skin of the initial nucleus and the mean-field potential in nucleon propagation are consistently treated. Our calculations show that the three observables, such as the cross-sections of the primary projectile-like residues with A>100 (σA>100), the difference of σA>100 between 132Sn + 124Sn and 124Sn + 124Sn systems (δσA>100), and the neutron-to-proton yield ratio (R(n/p)) in the transverse direction, could be used to measure the neutron skin of the unstable nuclei and to constrain the slope of the symmetry energy in the future.

Infinite nuclear matter is a suitable laboratory to learn about nuclear forces in many-body systems. In particular, modern theoretical predictions of neutron-rich matter are timely because of recent and planned experiments aimed at constraining the equation of state of isospin-asymmetric matter. For these reasons, we have taken a broad look at the equation of state of neutron-rich matter and the closely related symmetry energy, which is the focal point of this article. Its density dependence is of paramount importance for a number of nuclear and astrophysical systems, ranging from neutron skins to the structure of neutron stars. We review and discuss ab initio predictions in relation to recent empirical constraints. We emphasize and demonstrate that free-space nucleon–nucleon data pose stringent constraints on the density dependence of the neutron matter equation of state, which essentially determines the slope of the symmetry energy at saturation.

We report predictions for the neutron skin in 208Pb using chiral two- and three-body interactions at increasing orders of chiral effective field theory and varying resolution scales. Closely related quantities, such as the slope of the symmetry energy, are also discussed. The sensitivity of the skin to just pure neutron matter pressure when going from order 2 to order 4 of chiral effective theory is singled out in a set of calculations that employ an empirical equation of state for symmetric nuclear matter.

We report predictions for the neutron skin in 208Pb using chiral two- and three-body interactions at increasing orders of chiral effective field theory and varying resolution scales. Closely related quantities, such as the slope of the symmetry energy, are also discussed. The sensitivity of the skin to just pure neutron matter pressure when going from order 2 to order 4 of chiral effective theory is singled out in a set of calculations that employ an empirical equation of state for symmetric nuclear matter. [ABSTRACT FROM AUTHOR]

The mass-dependent symmetry energy coefficients a(A) has been extracted by analysing the heavy nuclear mass differences reducing the uncertainties as far as possible in our previous work. Taking advantage of the obtained symmetry energy coefficient a(A) and the density profiles obtained by switching off the Coulomb interaction in Pb, we calculated the slope parameter L of the symmetry energy at the density of 0.11 fm. The calculated L ranges from 40.5 MeV to 60.3 MeV. The slope parameter L of the symmetry energy at the density of 0.11 fm is also calculated directly with Skyrme interactions for nuclear matter and is found to have a fine linear relation with the neutron skin thickness of Pb, which is the difference of the neutron and proton rms radii of the nucleus. With the linear relation the neutron skin thickness Δ R of Pb is predicted to be 0.15-0.21 fm. [ABSTRACT FROM AUTHOR]

The nature of equation of state for the neutron star matter is crucially governed by the density dependence of the nuclear symmetry energy. We attempt to probe the behaviour of the nuclear symmetry energy around the saturation density by exploiting the empirical values for volume and surface symmetry energy coefficients extracted from the precise data on the nuclear masses. [ABSTRACT FROM AUTHOR]

We analyze theoretically the neutron skin thickness in nuclei and its correlation with the symmetry energy by using semiclassical and mean field approaches together with nuclear effective interactions. Semiclassical approaches reveal that the neutron skin thickness in nuclei is formed by a combination of bulk and surface contributions. To investigate the neutron skin thickness predicted by mean field models, we fit the corresponding densities by two-parameter Fermi distributions. Using these parametrized densities, we study the neutron skin thickness as well as its bulk and surface contributions in 208Pb and in Zr isotopes, where the influence of shell effects along the isotopic chain is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The collective multipole response of neutron-proton asymmetric nuclei has been investigated experimentally so far mainly utilizing the heavy-ion induced electromagnetic excitation. The experimental findings concerning the dipole strength in neutron-rich nuclei are summarized and a brief outlook is given. [Copyright &y& Elsevier]

Abstract: Binding energy of isospin asymmetric nuclei can be accessed with minimally modified formula along the lines of the liquid droplet model by partitioning the symmetry term into volume and surface terms. The volume symmetry energy coefficient extracted from finite nuclei provides a constraint on the nuclear symmetry energy. This approach also yields the neutron skin of a finite nucleus through its relationship with the volume and surface symmetry terms and the Coulomb energy coefficient. The symmetry energy at saturation density obtained from the isoscalar as well as isovector components of the density dependent M3Y effective interaction is found to be in close agreement with the volume symmetry energy coefficient extracted from the measured atomic masses. [Copyright &y& Elsevier]