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 the inflation field is responsible for the accelerated expansion
of the universe. Potentials of the selfinteracting 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 stan
dard 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 accel
erated expansion of the universe where the inflaton rolls nearly steep potential and the
universe will be radiation dominated without any separated reheating epoch.
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