The role of fluctuation-dissipation dynamics in setting initial
  conditions for inflation
  We study the problem of initial conditions for slow-roll inflation along a
plateau-like scalar potential within the framework of fluctuation-dissipation
dynamics. We consider, in particular, that inflation was preceded by a
radiation-dominated epoch where the inflaton is coupled to light degrees of
freedom and may reach a near-equilibrium state. We show that the homogeneous
field component can be sufficiently localized at the origin to trigger a period
of slow-roll if the interactions between the inflaton and the thermal degrees
of freedom are sufficiently strong and argue that this does not necessarily
spoil the flatness of the potential at the quantum level. We further conclude
that the inflaton can still be held at the origin after its potential begins to
dominate the energy balance, leading to a period of thermal inflation. This
then suppresses the effects of nonlinear interactions between the homogeneous
and inhomogeneous field modes that could prevent the former from entering a
slow-roll regime. Finally, we discuss the possibility of an early period of
chaotic inflation, at large field values, followed by a first stage of
reheating and subsequently by a second inflationary epoch along the plateau
about the origin. This scenario could prevent an early overclosure of the
Universe, at the same time yielding a low tensor-to-scalar ratio in agreement
with observations.
