  The equation of state (EOS) of dense matter and neutrino mean free path
(NMFP) in a neutron star have been studied by using relativistic mean field
models motivated by effective field theory (ERMF). It is found that the models
predict too large proton fractions, although one of the models (G2) predicts an
acceptable EOS. This is caused by the isovector terms. Except G2, the other two
models predict anomalous NMFP. In order to minimize the anomaly, besides an
acceptable EOS, a large M* is favorable. A model with large M* retains the
regularity in the NMFP even for a small neutron fraction.
