  The potential $V(\phi)=\lambda \phi^{n}$ is responsible for the inflation of
the universe as scalar field $\phi$ oscillates quickly around some point where
$V(\phi)$ has a minimum. The end of this stage has an important role on the
further evolution stages of the universe. The created particles are responsible
for reheating the universe at the end of this stage. The behaviour of the
inflation and reheating stages are often known as power law expansion $S(\eta)
\varpropto \eta^{1+\beta}$, $S(\eta) \varpropto \eta^{1+\beta_{s}}$
respectively. The reheating temperature ($T_{rh}$) and $\beta_{s}$ give us
valuable information about the reheating stage. Recently people have studied
about the behaviour of $T_{rh}$ based on slow-roll inflation and initial
condition of quantum normalization. It is shown that there is some discrepancy
on $T_{rh}$ due to amount of $\beta_{s}$ under the condition of slow-roll
inflation and quantum normalization \cite{acq}. Therefore the author is
believed in \cite{acq} that the quantum normalization may not be a good initial
condition. But it seems that we can remove this discrepancy by determining the
appropriate parameter $\beta_{s}$ and hence the obtained temperatures based on
the calculated $\beta_{s}$ are in favour of both mentioned conditions. Then
from given $\beta_{s}$, we can calculate $T_{rh}$, tensor to scalar ratio $r$
and parameters $\beta, n$ based on the Planck and WMAP-9 data. The observed
results of $r, \beta_{s}, \beta$ and $n$ have consistency with their
constrains. Also the results of $T_{rh}$ are in agreement with its general
range and special range based on the DECIGO and BBO detectors.
