  It is shown that the vacuum condensate induced by many phenomena behaves as a
perfect fluid which, under particular conditions, has zero or negative
pressure. In particular, the condensates of thermal states, of fields in curved
space and of mixed particles have been analyzed. It is shown that the thermal
states with the cosmic microwave radiation temperature, the Unruh and the
Hawking radiations give negligible contributions to the critical energy density
of the universe, while the thermal vacuum of the intercluster medium could
contribute to the dark matter, together with the vacuum energy of fields in
curved space-time and of mixed neutrinos. Moreover, a component of the dark
energy can be represented by the vacuum of axion-like particles mixed with
photons and superpartners of neutrinos. The formal analogy among the systems
characterized by the condensates can open new scenarios in the possibility to
detect the dark components of the universe in table top experiments.
