The Preheating Stage on The Starobinsky Inflation after ACT

Abstract: In this paper, we reinvestigate the Starobinsky inflation and its reheating features after the ACT results. To make the Starobinsky model satisfy ACT with $68\%$ CL, the number of e-folds increases to $>70$ while the reheating temperature drops to $10^4$ GeV. The preheating stages and the reheating temperature need to be adjusted drastically in favor of the lower temperature. We obtain that the preheating stage of Starobinsky inflation should be mixed between tachyonic and non-tachyonic preheating to favor the analytical estimation, PBH abundance, and the low reheating temperature at once. For that purpose, a varied momentum is necessary to obtain the favored results.