Quasi Goldstone fermion as a sterile neutrino.

The existence of sterile neutrino is hinted by simultaneous explanation of diverse neutrino anomalies. We suggest that the quasi Goldstone fermions (QGF) arising in supersymmetric theory as a result of spontaneous breaking of global symmetry like the Peccei-Quinn symmetry or the lepton number symmetry can play a role of the sterile neutrino. The smallness of mass of QGF (mS ∼ 10 − 10 eV) can be related to the specific choice of superpotential or Kähler potential (e.g., noscale kinetic terms for certain superfields). Mixing of QGF with neutrinos implies the R-parity violation. It can proceed via the coupling of QGF with the Higgs supermultiplets or directly with the lepton doublet. A model which accounts for the solar and atmospheric anomalies and the dark matter is presented.