  A thermal squeezed state representation of inflaton is constructed for a flat
Friedmann-Robertson-Walker background metric and the phenomenon of particle
creation is examined during the oscillatory phase of inflaton, in the
semiclassical theory of gravity. An approximate solution to the semiclassical
Einstein equation is obtained in thermal squeezed state formalism by
perturbatively and is found obey the same power-law expansion as that of
classical Einstein equation. In addition to that the solution shows oscillatory
in nature except on a particular condition. It is also noted that, the
coherently oscillating nonclassical inflaton, in thermal squeezed vacuum state,
thermal squeezed state and thermal coherent state, suffer particle production
and the created particles exhibit oscillatory behavior. The present study can
account for the post inflation particle creation due to thermal and quantum
effects of inflaton in a flat FRW universe.
