Neutrino Mass Sum-rules in Flavor Symmetry Models
  Four different neutrino mass sum-rules have been analyzed: these frequently
arise in flavor symmetry models based on the groups A_4, S_4 or T', which are
often constructed to generate tri-bimaximal mixing. In general, neutrino mass
can be probed in three different ways, using beta decay, neutrino-less double
beta decay and cosmology. The general relations between the corresponding three
neutrino mass observables are well known. The sum-rules lead to relations
between the observables that are different from the general case and therefore
only certain regions in parameter space are allowed. Plots of the neutrino mass
observables are given for the sum-rules, and analytical expressions for the
observables are provided. The case of deviations from the exact sum-rules is
also discussed, which can introduce new features. The sum-rules could be used
to distinguish some of the many models in the literature, which all lead to the
same neutrino oscillation results.
