Dark energy condensate and vacuum energy
  Many candidate models for dark energy are based on the existence of a
classical scalar field. In the context of Quantum Field Theory (QFT), we
briefly discus the condensation of such a field from a light quantum scalar
field produced by gradual decay of a heavy particle during cosmological time.
We obtain the necessary conditions for survival of the condensate in an
expanding universe and show that this process is directly related to quantum
nature of the field which preserves the coherence of the condensate at
cosmological distances. We also suggest a new interpretation of {\it vacuum
energy} in QFT in curved space time which can potentially solve the puzzle of
huge deviation of what is considered to be the vacuum energy from observations
of dark energy.
