Towards the minimal seesaw model via CP violation of neutrinos

We study the minimal seesaw model, where two right-handed Majorana neutrinos are introduced, focusing on the CP violating phase. In addition, we take the trimaximal mixing pattern for the neutrino flavor where the charged lepton mass matrix is diagonal. Thanks to this symmetric framework, the $3\times 2$ Dirac neutrino mass matrix is given in terms of a few parameters. Numerical studies reveal that the observation of the CP violating phase can determine the flavor structure of the Dirac neutrino mass matrix in the minimal seesaw model. In particular, new minimal Dirac neutrino mass matrices are proposed in the case of $\rm TM_1$, which is derived by the additional 2-3 family mixing to the tri-bimaximal mixing basis in the normal hierarchy of neutrino masses. Our analyses include the Littlest seesaw model by King {\it et al.}, which is one of the specific one in our results. Furthermore, it is remarked that our $3\times 2$ Dirac neutrino mass matrix is reproduced by introducing gauge singlet flavons with the specific alignments of the VEV's. These alignments suggest the residual symmetry of $S_4$ group.Comment: 27 pages, 27 figures, final versio

レプトン世代混合の現象論

広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora

Neutrino CP violation and sign of baryon asymmetry in the minimal seesaw model

We discuss the correlation between the CP violating Dirac phase of the lepton mixing matrix and the cosmological baryon asymmetry based on the leptogenesis in the minimal seesaw model with two right-handed Majorana neutrinos and the trimaximal mixing for neutrino flavors. The sign of the CP violating Dirac phase at low energy is fixed by the observed cosmological baryon asymmetry since there is only one phase parameter in the model. According to the recent T2K and NO$\nu$A data of the CP violation, the Dirac neutrino mass matrix of our model is fixed only for the normal hierarchy of neutrino masses.Comment: 19 pages, 4 figures, 1 table. 1 reference is added in this version. arXiv admin note: text overlap with arXiv:1709.0213

Deformations of log terminal and semi log canonical singularities

In this paper, we prove that klt singularities are invariant under a deformation over a (not necessarily one-dimensional) smooth base if the generic fiber is $\mathbb{Q}$-Gorenstein. We obtain a similar result for slc singularities when the base is one-dimensional. These are generalizations of results of Esnault-Viehweg and S. Ishii.Comment: 42pages. arXiv admin note: text overlap with arXiv:2103.0372