  The evolution of the universe started from a hot and dense Big Bang point.
Temperature fluctuation map of cosmic microwave background (CMB) radiation and
initial seeds of large scale structures (LSS) are explained by an inflationary
period in a very early time. Inflaton as quanta of inflation field is
responsible for the accelerated expansion of the universe. Potentials of the
self-interacting single field models are constrained by observational data as
well as quantum gravity. Some forms of the potential are rolled out by data of
Planck satellite and some of them by quantum gravity constraints. In the
standard model of inflation or cold inflation firstly universe expands where
the inflaton rolls the nearly flat part of the potential and in the second
part, the universe reheats where the inflaton oscillates around the minimum of
the potential which leads to thermalized radiation dominated universe. String
theory as the best model of quantum gravity forbids the oscillation around the
minimum of the potential during the thermalized epoch of the reheating. But in
the warm model of inflation thermalization happens during the expansion of the
universe where the inflaton rolls nearly steep potential and the universe will
be radiation dominated without any separated reheating epoch.
