From general Fermi liquid theory arguments, we derive correlations among the symmetry energy (J), its slope parameter (L), and curvature (Ksym) at nuclear matter saturation density. We argue that certain properties of these correlations do not depend on details of the nuclear forces used in the calculation. We derive as well a global parametrization of the density dependence of the symmetry energy that we show is more reliable, especially at low densities, than the usual Taylor series expansion around saturation density. We then benchmark these predictions against explicit results from chiral effective field theory.
PACS numbers:The nuclear isospin-asymmetry energy, which characterizes the energy cost of converting protons into neutrons in an interacting many-body system, is an important organizing concept linking the properties of atomic nuclei to the structure and dynamics of neutron stars. In particular the isospin-asymmetry energy governs the proton fraction of dense matter in beta equilibrium, the thickness of neutron star crusts, and the typical radii of neutron stars [1][2][3][4][5][6]. For these reasons the nuclear isospinasymmetry energy is a primary focus of experimental investigations at current and next-generation rare-isotope facilities such as the Radioactive Isotope Beam Factory (RIBF), the Facility for Antiproton and Ion Research (FAIR), and the Facility for Rare Isotope Beams (FRIB).In recent years, theoretical [6-10] and experimental [11][12][13][14][15] studies have reduced the uncertainties on the isospin-asymmetry energy at and below the density scales of normal nuclei, but more challenging is to derive constraints at the higher densities reached in the cores of neutron stars. Given the experimental difficulties of creating and studying high-density, low-temperature matter in the lab, an alternative strategy has been to extract the coefficients in the Taylor series expansion of the isospinasymmetry energy about nuclear matter saturation density. For instance, the slope parameter has been shown to correlate strongly with neutron skin thicknesses in nuclei [13,16,17], nuclear electric dipole polarizabilities [18-23], and the difference in charge radii of mirror nuclei [24,25]. Determining the isospin-asymmetry energy curvature is more challenging [26-28] with larger associated uncertainties.A feature observed in many experimental and theoretical investigations is a nearly linear correlation between the value of the isospin-asymmetry energy at nuclear matter saturation density, its slope, and curvature (for a recent comprehensive analysis, see Ref. [29]). In Ref.[10] it was shown that even chiral nuclear potentials at * Electronic address: holt@physics.tamu.edu † Electronic address: ylim@tamu.edu next-to-leading order (NLO), which are rather simplistic and contain no three-body forces, exhibit a correlation slope consistent with previous microscopic calculations at N2LO and N3LO in the chiral expansion. This suggests that certain aspects of the correlation are ultimately associated with low-ener...