Perturbative Reheating in the Mixed Higgs-$R^2$ Model
  The preheating process in the mixed Higgs-$ R^2 $ model has been investigated
in depth recently, but the analysis of perturbative reheating is still missing.
In this paper, we discuss the effect of perturbative decay during (p)reheating
in this model. It is shown that perturbative decay can play an important role
throughout the whole reheating process. Depending on the model parameters,
perturbative decay can affect different stages of the reheating. We study the
perturbative reheating with and without the presence of early preheating stage,
and calculate the reheating temperature and the duration of the whole
perturbative process. We find that the detail of the early preheating stage may
not affect the final reheating temperature while it can affect the number of
e-folds of reheating.
