
VOLUME 78 (2003)  ISSUE 11 
PAGE 1203

Dark matter from SU(4) model
G. E. Volovik
Low Temperature Laboratory, Helsinki University of Technology, FIN02015 HUT, Finland L. D. Landau Institute for Theoretical Physics RAS, 117334 Moscow, Russia
PACS: 12.10.g, 12.60.Rc, 95.35.+d
Abstract
The leftright symmetric PatiSalam model of the
unification of quarks and leptons is based on SU(4) and SU(2)× SU(2)
symmetry groups. These groups are naturally extended to include the
classification
of families of quarks and leptons. We assume that the family group
(the group which
unites the families) is also the SU(4) group. The properties of
the fourthgeneration of fermions are the same as that of the ordinarymatter
fermions in first three generations except for the family charge of the
SU(4)_{F} group:
F=(1/3,1/3,1/3,1), where F=1/3 for fermions of
ordinary matter and F=1 for the fourthgeneration fermions. The
difference in
F does not allow the mixing between ordinary and fourthgeneration fermions.
Because of the conservation of the
F charge, the creation of baryons and leptons in the process of electroweak
baryogenesis must be accompanied by the creation of fermions of the 4th
generation. As a result the
excess n_{B} of baryons over antibaryons leads to the excess
of neutrinos over antineutrinos in the 4th generation with
n_{4ν}= n_{B}.
This massive neutrino may form the nonbaryonic dark matter. In
principle the mass density of the 4th neutrino
n_{4ν} m_{N} in the Universe can give the main contribution to the dark
matter, since the lower bound on the neutrino mass m_{N} from the
data on decay of
the
Zbosons is
m_{N}>m_{Z}/2. The straightforward prediction of this model leads
to the amount of cold dark matter relative to baryons, which is an order of
magnitude bigger than allowed by observations. This inconsistency may
be avoided
by nonconservation of the
Fcharge.

