Cosmological dynamics of dark matter Bose-Einstein Condensation
  Once the critical temperature of a cosmological boson gas is less than the
critical temperature, a Bose-Einstein Condensation process can always take
place during the cosmic history of the universe. In the Bose-Einstein
Condensation model, dark matter can be described as a non-relativistic,
Newtonian gravitational condensate, whose density and pressure are related by a
barotropic equation of state, with barotropic index equal to one. In the
present work, we study the Bose-Einstein Condensation process in a cosmological
context, by assuming that this process can be described (at least
approximately) as a first order phase transition. We analyze the evolution of
the physical quantities relevant for the physical description of the early
universe, namely, the energy density, temperature and scale factor, before,
during and after the Bose-Einstein Condensation (phase transition). We also
consider in detail the epoch when the universe evolved through a mixed
condensate - normal dark matter phase, with a monotonically growing
Bose-Einstein dark matter component. An important parameter characterizing the
Bose-Einstein Condensation is the condensate dark matter fraction, whose time
evolution describes the time dynamics of the conversion process. The behavior
of this parameter during the cosmological condensation process is also analyzed
in detail. To study the cosmological dynamics and evolution we use both
analytical and numerical methods. The presence of the condensate dark matter
and of the Bose-Einstein phase transition could have modified drastically the
cosmological evolution of the early universe, as well as the large scale
structure formation process.
