Phenomenological neutrino mass matrix for neutrino oscillations and dark matter

A phenomenological neutrino mass matrix is proposed to explain the solar and atmospheric neutrino deficits and to present the neutrino as a candidate of hot dark matter in the $3{\nu }_L+3{\nu }_R$ framework. The realization of mixing angles which can explain the solar and atmospheric neutrino problems is taken as the first criterion in this construction. The differences among neutrino mass eigenvalues are introduced as a perturbation. In this scheme the structure of a charged lepton mass matrix is not severely constrained by the solar and atmospheric neutrino data.