  Models with low-scale breaking of global symmetries in the neutrino sector
provide an alternative to the seesaw mechanism for understanding why neutrinos
are light. Such models can easily incorporate light sterile neutrinos required
by the LSND experiment. Furthermore, the constraints on the sterile neutrino
properties from nucleosynthesis and large scale structure can be removed due to
the non-conventional cosmological evolution of neutrino masses and densities.
We present explicit, fully realistic supersymmetric models, and discuss the
characteristic signatures predicted in the angular distributions of the cosmic
microwave background.
