Large neutrino mixing from renormalization group evolution

The renormalization group evolution equation for two neutrino mixing is known to exhibit a nontrivial “fixed point” structure corresponding to maximal mixing at the weak scale. Their presence provides a natural explanation of the observed maximal mixing of ${\nu }_{\mu }-{\nu }_{\tau }$ if the ${\nu }_{\mu }$ and ${\nu }_{\tau }$ are assumed to be quasidegenerate at the seesaw scale without constraining the mixing angles at that scale. In particular, it allows them to be similar to the quark mixings as in generic grand unified theories. We discuss implementation of this program in the case of the minimal supersymmetric standard model and find that the predicted mixing remains stable and close to its maximal value, for all energies below the O (TeV) SUSY scale. We also discuss how a particular realization of this idea can be tested in neutrinoless double beta decay experiments.