A Light Sterile Neutrino in the TopFlavor Model
  A scenario based on the TopFlavor model is presented to explain the origin of a light sterile neutrino as indicated by all combined neutrino oscillation experiments. The model is phenomenologically well motivated and compatible with all available low-energy data. The derived nuetrino mass matrix can qualitatively explain the observed hierarchy in the neutrino mass splittings as indicated by the neutrino oscillation data. Numerical results are obtained for special cases. 
Ehab Malkawi (JUST, Jordan), E.I. Lashin (Cario, Eygpt), Hatem Widyan   (JUST, Jordan)