  Core collapse supernovae are dominated by energy transport from neutrinos.
Therefore, some supernova properties could depend on symetries and features of
the standard model weak interactions. The cross section for neutrino capture is
larger than that for antineutrino capture by one term of order the neutrino
energy over the nucleon mass. This reduces the ratio of neutrons to protons in
the $\nu$-driven wind above a protoneutron star by approximately 20 % and may
significantly hinder r-process nucleosynthesis.
