A different see-saw formula for neutrino masses

In a wide class of unified models there is an additional (and possibly dominant) term in the neutrino mass formula that under the simplest assumption takes the form M_{\nu} = (M_N + M_N^T)u/M_G, where M_N is the neutrino Dirac mass matrix, and u = O(M_W). This makes possible highly predictive models. A generalization of this form yields realistic neutrino masses and mixings more readily than the usual see-saw formula in some models.