W. G. Newton, M. Gearheart, Bao-An Li
Within the liquid drop model, and using a phenomenological Skyrme-like
parameterization of the uniform nuclear matter equation of state (EoS), we
first construct a set of `baseline' crustal equations of state that span the
experimentally constrained values of the symmetry energy at nuclear saturation
density, as well as the theoretically constrained region of the pure neutron
matter (PNM) EoS at low density. The resulting range of crustal compositional
parameters relevant for macroscopic models of the crust is explored, as well as
the crust-core transition densities and pressures and the density range of the
`pasta' phases of nuclei at the bottom of the crust. We explore the deviation
of these parameters from the baseline models as a result of the remaining
experimental uncertainties in the symmetric nuclear matter (SNM) EoS and the
parameterization of the surface energy in the liquid drop model. The transition
densities and pressures are found to be quite sensitive to the behavior of the
surface tension \emph{at very low proton fractions}; recent calculations of the
energies of neutron drops suggest that this might be higher than previously
thought, which our study suggests may result in a much reduced volume of pasta
in the crust. Most crustal compositional parameters are shown to be insensitive
to the SNM EoS and the surface energy relative to the uncertainties in the
symmetry energy, with the notable exception of the size of the nuclei which
show a similar dependence on all the model parameters. We establish a set of
crustal equations of state which can be matched with any core EoS based upon
the symmetry energy and its derivative, allowing a consistent exploration of
the dependence on the symmetry energy of global crustal models and potentially
observable phenomena such as pulsar glitches and oscillation modes that
incorporate a coupling between crust and core.
View original:
http://arxiv.org/abs/1110.4043
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