  We have performed three-flavor Boltzmann neutrino transport radiation
hydrodynamics simulations covering a period of 3 s after the formation of a
protoneutron star in a core-collapse supernova explosion. Our results show that
a treatment of charged-current neutrino interactions in hot and dense matter as
suggested by Reddy et al. [Phys. Rev. D 58, 013009 (1998)] has a strong impact
on the luminosities and spectra of the emitted neutrinos. When compared with
simulations that neglect mean field effects on the neutrino opacities, we find
that the luminosities of all neutrino flavors are reduced while the spectral
differences between electron neutrino and antineutrino are increased. Their
magnitude depends on the equation of state and in particular on the symmetry
energy at sub-nuclear densities. These modifications reduce the
proton-to-nucleon ratio of the outflow, increasing slightly their entropy. They
are expected to have a substantial impact on the nucleosynthesis in
neutrino-driven winds, even though they do not result in conditions that favor
an r-process. Contrarily to previous findings, our simulations show that the
spectra of electron neutrinos remain substantially different from those of
other (anti)neutrino flavors during the entire deleptonization phase of the
protoneutron star. The obtained luminosity and spectral changes are also
expected to have important consequences for neutrino flavor oscillations and
neutrino detection on Earth.
