High Energy Theory Lunchtime Seminar

The current experimental values for neutrino mixing angles are very close to the predictions of the so-called ``tri-bimaximal'' mixing matrix. I will describe a recent model which gives rise to, for the first time, the tri-bimaximal neutrino mixing and realistic quark CKM matrix simultaneously. The model is based on SU(5) GUT combined with the double tetrahedral group as a family symmetry, and it has only nine parameters to account for all 18 fermion masses and mixing angles. The model also predicts a new sum rule relating the solar mixing angle for the neutrinos and the Cabibbo angle in the quark sector, as a result of the Georgi-Jarlskog relations. The double tetrahedral group may be originated from extra dimensions as a residual symmetry upon orbifold compactification.