  We demonstrate that a stable particle with flavor mixing, confined in a
gravitational potential can gradually and irreversibly escape -- or "evaporate"
-- from it. This effect is due to mass eigenstate conversions which occur in
interactions (scattering) of mass states with other particles even when the
energy exchange between them is vanishing. The evaporation and conversion are
quantum effects not related to flavor oscillations, particle decay, quantum
tunneling or other well-known processes. Apart from their profound academic
interest, these effects should have tremendous implications for cosmology,
e.g., (1) the cosmic neutrino background distortion is predicted and (2) the
softening of central cusps in dark matter halos and smearing out or destruction
of dwarf halos were suggested.
