Inflationary universe in fluid description
  We investigate a fluid description of inflationary cosmology. It is shown
that the three observables of the inflationary universe: the spectral index of
the curvature perturbations, the tensor-to-scalar ratio of the density
perturbations, and the running of the spectral index, can be compatible with
the Planck analysis. In addition, we reconstruct the equation of state (EoS)
for a fluid from the spectral index of the curvature perturbations consistent
with the Planck results. We explicitly demonstrate that the universe can
gracefully exit from inflation in the reconstructed fluid models. Furthermore,
we explore the singular inflation for a fluid model.
