  The idea that the Majorana neutrino should be identified as a Bogoliubov
quasiparticle is applied to the seesaw mechanism for the three generations of
neutrinos in the Standard Model. A relativistic analogue of the Bogoliubov
transformation in the present context is a CP-preserving canonical
transformation but modifies charge conjugation properties in such a way that
the C-noninvariant fermion number violating term (condensate) is converted to a
Dirac mass term. Puzzling aspects associated with the charge conjugation of
chiral Weyl fermions are clarified. By invoking the Coleman--Weinberg mechanism
in the framework of dimensional regularization, it is also noted that seesaw
models become unnatural in some parameter regions which induce the hierarchy
problems in the bosonic sector.
