Kinetic Equilibration after Preheating
  We study thermal equilibration after preheating in inflationary cosmology,
which is an important step towards a comprehensive understanding of cosmic
thermal history. By noticing that the problem is parallel to thermalization
after a relativistic heavy ion collision, we make use of the methods developed
in this context and that seek for an analytical approach to the Boltzmann
equation. In particular, an exact solution for number-conserving scatterings is
available for the distribution function in a
Friedmann-Lema\^{i}tre-Robertson-Walker metric and can be utilized for the
spectral evolution of kinetic equilibration process after preheating. We find
that thermal equilibration is almost instantaneous on the time scale of the
Hubble time. We also make an explicit prediction for the duration (the number
of e-folds of expansion) required for this process of thermal equilibration to
complete following the end of inflation.
