Model dependence of the neutron-skin thickness on the symmetry energy

Abstract

The model dependence in the correlations of the neutron-skin thickness in heavy nuclei with various symmetry energy parameters is analyzed by using several families of systematically varied microscopic mean field models. Such correlations show a varying degree of model dependence once the results for all the different families are combined. Some mean field models associated with similar values of the symmetry energy slope parameter at saturation density $L$, and pertaining to different families, yield a greater-than-expected spread in the neutron-skin thickness of the $^{208}$Pb nucleus. The effective value of the symmetry energy slope parameter $L_{\rm eff}$, determined by using the nucleon density profiles of the finite nucleus and the density derivative $S^\prime(\rho)$ of the symmetry energy starting from about saturation density up to low densities typical of the surface of nuclei, seems to account for the spread in the neutron-skin thickness for the models with similar $L$. The differences in the values of $L_{\rm eff}$ are mainly due to the small differences in the nucleon density distributions of heavy nuclei in the surface region and the behavior of the symmetry energy at subsaturation densities.Comment: 10 pages including 6 figure

Volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model

“…(9) and (10)] (e.g., from [40,41,48,50,51]), as expected, can be represented approximately in the form of Eq. (2):…”

Constraints on the nuclear equation of state from nuclear masses and radii in a Thomas-Fermi meta-modeling approach

“…It is however highly probable that many of such correlations might be spuriously induced by the insufficient exploration of the complex parameter hyper-surface, and the specific functional form assumed for the EoS, which as long as phenomenological models are used has always a certain degree of arbitrariness. The presence of spurious effects is clearly indicated by the fact that the correlation among empirical parameters are modified by changing the functional family, from Skyrme to Gogny or RMF or RHF [11,[14][15][16]18]. A simple example is given by non-relativistic functionals: it is easy to show analytically that the phenomenological density dependent term of Skyrme interactions induces artificial correlations among the different isoscalar as well as isovector EoS terms [15].…”

“…Consequently, one can expect that the EoS independent surface contribution to the skin should be sorted out in order to recover the correct correlation with the EoS. However, when using more sophisticated EoS models it was shown [18,20,21] that the surface contribution is remarkably constant in the different relativistic and non-relativistic models, and therefore the correlation of the skin with L sym is preserved. It was conjectured [20] that this constant behavior might come from the constraint on nuclear mass reproduction applied to the DFT functionals, but the argument neglects the fact that the mass itself is known to provide constraints on the EoS [4,10,22] besides the constraints on the finite size parameters [23] .…”

Diffusive heat blanketing envelopes of neutron stars

“…The basic problems are that (i) it is difficult to explore the superdense matter in terrestrial laboratories; (ii) its properties cannot be calculated reliably because of the absence of practical theory for describing strong interactions of baryons with account of many-body effects. Some properties of superdense matter can be studied in collider experiments on heavy ions collisions, on neutron skin measurements and in some other ways (e.g., Lattimer and Prakash 2016;Mondal et al 2016;Oertel et al 2017), but these data are incomplete. Very dense matter ( 10 4 0 ), which can appear after the deconfinement of quarks, can be analyzed by the methods of perturbative quantum chromodynamics (e.g., Haensel et al 2007;Machleidt and Entem 2011).…”