Neutrinos versus Quarks, MNS versus CKM

Abstract

We review recent developments in models of fermion masses and mixing for both quark and lepton sectors. Emphases are given to models based on finite group family symmetries. In particular, we describe one recent model based on SU(5) combined with a family symmetry based on the double tetrahedral group, T'. In this model, a near tri-bimaximal MNS matrix and a realistic CKM matrix are simultaneously generated; the MNS matrix gets slightly modified by virtue of having the Georgi-Jarlskog relations. Due to the presence of complex Clebsch-Gordon coefficients in T', CP violation in this model is entirely geometrical in origin.