Neutrinos and symmetries

Three facets of symmetries in neutrino physics are briefly reviewed: i) The SO(5) symmetry of the neutrino mass and and its connection to the see-saw mechanism; ii) SU(Nflavor) symmetries of dense, self-interacting neutrino gases in astrophysical settings; iii) The neutrino mixing angle θ13 and possible CP-violation in the neutrino sector.