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Low Densities Instability of Relativistic Mean Field Models
The effects of the symmetry energy softening of the relativistic mean field
(RMF) models on the properties of matter with neutrino trapping are
investigated. It is found that the effects are less significant than those in
the case without neutrino trapping. The weak dependence of the equation of
state on the symmetry energy is shown as the main reason of this finding. Using
different RMF models the dynamical instabilities of uniform matters, with and
without neutrino trapping, have been also studied. The interplay between the
dominant contribution of the variation of matter composition and the role of
effective masses of mesons and nucleons leads to higher critical densities for
matter with neutrino trapping. Furthermore, the predicted critical density is
insensitive to the number of trapped neutrinos as well as to the RMF model used
in the investigation. It is also found that additional nonlinear terms in the
Horowitz-Piekarewicz and Furnstahl-Serot-Tang models prevent another kind of
instability, which occurs at relatively high densities. The reason is that the
effective sigma meson mass in their models increases as a function of the
matter density.Comment: 25 pages, 10 figures, submitted to Phys. Rev.
Isovector Channel Role of Relativistic Mean Field Models in the Neutrino Mean Free Path
An improvement in the treatment of the isovector channel of relativistic mean
field (RMF) models based on effective field theory (E-RMF) is suggested, by
adding an isovector scalar (delta) meson and using a similar procedure to the
one used by Horowitz and Piekarewicz to adjust the isovector-vector channel in
order to achieve a softer density dependent symmetry energy of the nuclear
matter at high density. Their effects on the equation of state (EOS) at high
density and on the neutrino mean free path (NMFP) in neutron stars are
discussed.Comment: 20 pages, 8 figure
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