arXiv subjects
Publications and source records attributed to Ivo de Medeiros Varzielas.
Assuming high-energy tri-bi-maximal mixing we study the radiative running of leptonic mixing angles and obtain limits on the high-energy scale from requiring consistency with the observed mixing. We construct a model in which a non-Abelian discrete family symmetry leads both to a quasi-degenerate neutrino mass spectrum and to near tri-bi-maximal mixing.
We consider how, for quasi-degenerate neutrinos with tri-bi-maximal mixing at a high-energy scale, the mixing angles are affected by radiative running from high to low-energy scales in a supersymmetric theory. The limits on the high-energy scale that follow from consistency with the observed mixing are determined. We construct a model in which a non-Abelian discrete family symmetry leads both to a quasi-degenerate neutrino mass spectrum and to near tri-bi-maximal mixing.
Family symmetries are possibly the most conservative extension of the Standard Model that attempt explanations of the pattern of fermion masses and mixings. The observed large mixing angles in the lepton sector may be the first signal for the presence of a non-Abelian family symmetry. We investigate the possibilities of simultaneously explaining the observed pattern of masses of the quarks (hierarchical masses and small mixing angles) and of the leptons (near tri-bi-maximal mixing, thus large mixing angles). We show that such contrasting observations can be achieved naturally via the seesaw mechanism, whether in models with continuous or discrete family symmetries. We consider also in some detail the constraints on flavour changing neutral currents arising from introducing a continuous family symmetry. We show that, for a restricted choice of the flavon sector, continuous family symmetries are consistent with even the most conservative limits both for the case of gauge mediated supersymmetry breaking and the case of gravity mediated supersymmetry breaking.
The observed large mixing angles in the lepton sector may be the first signal for the presence of a non-Abelian family symmetry. However, to obtain the significant differences between the mixing of the neutrino and charged fermion sectors, the vacuum expectation values involved in the breaking of such a symmetry in the two sectors must be misaligned. We investigate how this can be achieved in models with an SU(3) family symmetry consistent with an underlying GUT. We show that such misalignment can be achieved naturally via the see-saw mechanism. We construct a specific example in which the vacuum (mis)alignment is guaranteed by additional symmetries. This model generates a fermion mass structure consistent with all quark and lepton masses and mixing angles. Neutrino mixing is close to bi-tri-maximal mixing.