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Renormalization group (RG) evolution of the neutrino mass matrix may take the value of the mixing angle $theta_{13}$ very close to zero, or make it vanish. On the other hand, starting from $theta_{13}=0$ at the high scale it may be possible to generate a non-zero $theta_{13}$ radiatively. In the most general scenario with non-vanishing CP violating Dirac and Majorana phases, we explore the evolution in the vicinity of $theta_{13}=0$, in terms of its structure in the complex ${cal U}_{e3}$ plane. This allows us to explain the apparent singularity in the evolution of the Dirac CP phase $delta$ at $theta_{13}=0$. We also introduce a formalism for calculating the RG evolution of neutrino parameters that uses the Jarlskog invariant and naturally avoids this singular behaviour. We find that the parameters need to be extremely fine-tuned in order to get exactly vanishing $theta_{13}$ during evolution. For the class of neutrino mass models with $theta_{13}=0$ at the high scale, we calculate the extent to which RG evolution can generate a nonzero $theta_{13}$, when the low energy effective theory is the standard model or its minimal supersymmetric extension. We find correlated constraints on $theta_{13}$, the lightest neutrino mass $m_0$, the effective Majorana mass $m_{ee}$ measured in the neutrinoless double beta decay, and the supersymmetric parameter $tanbeta$.
We propose an extension of tri-bimaximal mixing to include a non-zero reactor angle $theta_{13}$ while maintaining the tri-bimaximal predictions for the atmospheric angle $theta_{23}=45^o$ and solar angle $theta_{12}=35^o$. We show how such tri-bimax
The recent T2K, MINOS and Double Chooz oscillation data hint a relatively large $theta_{13}$, which can be accommodated by some general modification of the Tribimaximal/Bimaximal/Democratic mixing matrices. Using such matrices we analyze several Majo
In the Higgs Triplet Model and the neutrinophilic Two-Higgs-Doublet Model the observed neutrinos obtain mass from a vacuum expectation value which is much smaller than the vacuum expectation value of the Higgs boson in the Standard Model. Both models
We present the correlation of low energy CP phases, both Dirac and Majorana, and the lepton asymmetry for the baryon asymmetry in the universe, with a certain class of Yukawa matrices that consist of two right-handed neutrinos and include one texture
We study the lepton flavor models with the flavor symmetry (Z_N times Z_N times Z_N)rtimes Z_3. Our models predict non-vanishing discrete values of theta_{13} as well as theta_{12} and theta_{23} depending on N. For certain values, our models realize