Is dark matter an illusion created by the gravitational polarization of
  the quantum vacuum?
  Assuming that a particle and its antiparticle have the gravitational charge
of the opposite sign, the physical vacuum may be considered as a fluid of
virtual gravitational dipoles. Following this hypothesis, we present the first
indications that dark matter may not exist and that the phenomena for which it
was invoked might be explained by the gravitational polarization of the quantum
vacuum by the known baryonic matter.
