Q_6 flavor symmetry model for the extension of the minimal standard
  model by three right-handed sterile neutrinos
  The extension of the minimal standard model by three right-handed sterile
neutrinos with masses smaller than the electroweak scale (nuMSM) is discussed
in a Q_6 flavor symmetry framework. The lightness of the keV sterile neutrino
and the near mass degeneracy of two heavier sterile neutrinos are naturally
explained by exploiting group properties of Q_6. A normal hierarchical mass
spectrum and an approximately mu-tau symmetric mass matrix are predicted for
three active neutrinos. Nonzero theta_{13} can be obtained together with a
deviation of theta_{23} from the maximality, where both mixing angles are
consistent with the latest global data including T2K and MINOS results.
Furthermore, the tiny active-sterile mixing is related to the mass ratio
between the lightest active and lightest sterile neutrinos.
