  Generally speaking, the existence of a superluminal neutrino can be
attributed either to re-entrant Lorentz violation at ultralow energy from
intrinsic Lorentz violation at ultrahigh energy or to spontaneous breaking of
fundamental Lorentz invariance (possibly by the formation of a fermionic
condensate). Re-entrant Lorentz violation in the neutrino sector has been
discussed elsewhere. Here, the focus is on mechanisms of spontaneous symmetry
breaking.
