Inflationary Constraints on the Van der Waals Equation of State
  In spite of the strong observational evidence suggesting a period of rapid
expansion in the early universe, the identity of the inflaton field that drove
this expansion remains elusive. Many inflaton candidate particles (both known
and hypothesized) have been proposed to explain the early accelerated expansion
of the universe. Other explanations for an era of rapid expansion in the early
universe have been proposed via modifications of gravity in one form or
another.
  In this paper, we consider the possibility of using a Van der Waals equation
of state to describe the early-time accelerated expansion of the universe. We
do not attempt to explain why the early universe may be filled with such a
fluid, but rather investigate what constraints may be placed on the parameters
which describe a Van der Waals fluid that sources an accelerated expansion in
the early universe. We consider three different versions of the Van der Waals
equation of state and constrain the parameters of each using CMB data. We find
that two of the models do not fit constraints from observation. A third model
may satisfy observational constraints, but only under very narrow
circumstances.
