Constraints on texture zero and cofactor zero models for neutrino mass

Imposing a texture or cofactorzero on the neutrino mass matrixreduces the number of independent parameters from nine to seven. Since five parameters have been measured, only two independent parameters would remain in such models. We find the allowed regions for single texture zero and single cofactorzero models. We also find strong similarities between single texture zero models with one mass hierarchy and single cofactorzero models with the opposite mass hierarchy. We show that this correspondence can be generalized to texture-zero and cofactor-zero models with the same homogeneous costraints on the elements and cofactors.