Defrosting in an Emergent Galileon Cosmology
  We study the transition from an Emergent Galileon condensate phase of the
early universe to a later expanding radiation phase. This "defrosting" or
"preheating" transition is a consequence of the excitation of matter
fluctuations by the coherent Galileon condensate, in analogy to how preheating
in inflationary cosmology occurs via the excitation of matter fluctuations
through coupling of matter with the coherent inflaton condensate. We show that
the "minimal" coupling of matter (modeled as a massless scalar field) to the
Galileon field introduced by Creminelli, Nicolis and Trincherini in order to
generate a scale-invariant spectrum of matter fluctuations is sufficient to
lead to efficient defrosting, provided that the effects of the non-vanishing
expansion rate of the universe are taken into account. If we neglect the
effects of expansion, an additional coupling of matter to the Galileon
condensate is required. We study the efficiency of the defrosting mechanism in
both cases.
