  Neutrinos emitted from near the surface of the hot proto-neutron star
produced by a supernova explosion may be subject to significant gravitational
redshift at late times. Electron antineutrinos decouple deeper in the
gravitational potential well of the neutron star than do the electron
neutrinos, so that the electron antineutrinos experience a larger redshift
effect than do the electron neutrinos. We show how this differential redshift
can increase the electron fraction Ye in the neutrino-heated ejecta from the
neutron star. Any r-process nucleosynthesis originating in the neutrino-heated
ejecta would require a low Ye, implying that the differential redshift effect
cannot be too large. In turn, this effect may allow nucleosynthesis to probe
the nuclear equation of state parameters which set the neutron star radius and
surface density scale height at times of order tpb = 10 to 25 s after core
bounce.
