  The possibility of radiative effects that are due to interaction of fermions
with a dense matter is investigated. Neutrino-antineutrino photo-production is
studied. The rate of this process is calculated in the Furry picture. It is
demonstrated that this effect does not disappear even if the medium refractive
index is assumed to be equal to unity. The rate obtained strongly depends on
the polarization states of the particles involved. This leads to evident
spatial asymmetries, which may have certain consequences observable in
astrophysical and cosmological studies.
