Nuclear symmetry energy: from nuclear extremes to neutron-star matter

Abstract

Extrapolations from nuclei to neutron stars hinge on the symmetry term in nuclear binding formulas. The term describes reduction in the binding associated with neutron-proton (np) imbalance. Regrettably, binding formulas in the literature commonly lack an intrinsic consistency with regard to the symmetry term. Our elementary considerations determine the universal macroscopic limit for the term and predict its weakening in light nuclei due to emergence of the nuclear asymmetry-skin. Experimental systematic of isobaric-analogue states allows for a determination of the volume and surface coefficients within the macroscopic limit of the symmetry term, disregarding any reminder of a binding formula. The results are next exploited to constrain the dependence of symmetry energy on nuclear density, essential for the neutron-star predictions.