The mixing angle as a function of neutrino mass ratio
  In the quark sector, we experience a correlation between the mixing angles and the mass ratios. A partial realization of the similar tie-up in the neutrino sector helps to constrain the parametrization of masses and mixing, and hints for a predictive framework. We derive five hierarchy dependent textures of neutrino mass matrix with minimum number of parameters ($\leq\,4$), following a model-independent strategy. 
Subhankar Roy and N.Nimai Singh
hep-ph