sin θ13 and neutrino mass matrix with an approximate flavor symmetry

For a neutrino mass matrix whose texture has an approximate flavor symmetry and where one has near degenerate neutrino mass, it is shown that the tribimaximal values for atmospheric angle sin2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ {\theta_{{23}}} = \frac{1}{2} $\end{document} and solar angle sin2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ {\theta_{{12}}} = \frac{1}{3} $\end{document} can be maintained even when the reactor angle θ13 ≠ 0. The non zero sin θ13 implies approximate νμ → −ντ symmetry instead of νμ → ντ symmetry.