Constraining the symmetry parameters of the nuclear interaction

James M. Lattimer, Yeunhwan Lim

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One of the major uncertainties in the dense matter equation of state has been the nuclear symmetry energy. The density dependence of the symmetry energy is important in nuclear astrophysics, as it controls the neutronization of matter in core-collapse supernovae, the radii of neutron stars and the thicknesses of their crusts, the rate of cooling of neutron stars, and the properties of nuclei involved in r-process nucleosynthesis. We show that fits of nuclear masses to experimental masses, combined with other experimental information from neutron skins, heavy ion collisions, giant dipole resonances, and dipole polarizabilities, lead to stringent constraints on parameters that describe the symmetry energy near the nuclear saturation density. These constraints are remarkably consistent with inferences from theoretical calculations of pure neutron matter, and, furthermore, with astrophysical observations of neutron stars. The concordance of experimental, theoretical, and observational analyses suggests that the symmetry parameters Sv and L are in the range 29.0-32.7 MeV and 40.5-61.9 MeV, respectively, and that the neutron star radius, for a 1.4 M star, is in the narrow window 10.7 km <R < 13.1 km (90% confidence). We can also set tight limits to the size of neutron star crusts and the fractional moment of inertia they contain, as well as the overall moment of inertia and quadrupole polarizability of 1.4 M stars. Our results also have implications for the disk mass and ejected mass of compact mergers involving neutron stars.

Original languageEnglish
Article number51
JournalAstrophysical Journal
Issue number1
StatePublished - 1 Jul 2013


  • dense matter
  • equation of state
  • stars: neutron


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