Power-law Inflation with Scalar Field assisted R² Gravity: a perturbative approach

It is shown that power-law inflation (PLI) in general relativity (GR)-based cosmology can be realized due to the f(R) gravity corrections to the standard GR action. In this paper, we have considered ϵR ² correction to the GR-based PLI model, and then apply the perturbation theory to first order to explore the effects of ϵR ² correction on the results obtained from GR-based PLI model. This model has the ability to resolve the problems arise in GR-based PLI model. We calculate scalar spectral index, tensor-to-scalar ratio, running of spectral index, which are in very good agreement with recent Planck2018 data. An interesting feature of this model is that it has a graceful exit to radiation-dominated stage which is induced by the ϵR ² correction. (paper)