  Dimensional reduction from 10 to 5 dimensions of the IIB supergravity Dirac
equation written down on the AdS(5)xS(5) (+ self-dual 5-form) background
provides the unambiguous values of bulk masses of Fermions in the effective 5D
Randall Sundrum theory. The use of "untwisted" and "twisted" (hep-th/0012378)
boundary conditions at the UV and IR ends of the warped space-time results in
two towers of spectrum of Dirac equation: the ordinary one which is linear in
spectral number and the "twisted" one exponentially decreasing with growth of
spectral number. Taking into account of the Fermion-5-form interaction
(hep-th/9811106) gives the electron neutrino mass scale in the "twisted"
spectrum of Dirac equation. Profiles in extra space of the eigenfunctions of
left and right "neutrinos" drastically differ which may result in the extremely
small coupling of light right neutrino with ordinary matter thus joining it to
plethora of candidates for Dark Matter.
