Slow-roll inflation in f (R, T) gravity and a modified Starobinsky-like inflationary model

In this work, we studied the slow-roll approximation of cosmic inflation within the context of f (R,T) gravity, where R is the scalar curvature, and T is the trace of the energy-momentum tensor. By choosing a minimal coupling between matter and gravity, we obtained the modified slow-roll parameters, the scalar spectral index (n(s)), the tensor spectral index (n(T)), and the tensor-to-scalar ratio (r). We computed these quantities for a general power-law potential, Natural & Quartic Hilltop inflation, and the Starobinsky model, plotting the trajectories on the (n(s), r) plane. We found that one of the parameters of Natural/Hilltop models is non-trivially modified. Besides, if the coupling is in the interval -0.5 < alpha < 5.54, we concluded that the Starobinsky-like model predictions are in good agreement with the last Planck measurement, but with the advantage of allowing a wide range of admissible values for r and nT. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study focused on the slow-roll approximation of cosmic inflation within the framework of f (R,T) gravity. By analyzing different models and computing various parameters, it was found that the predictions of the Starobinsky-like model are in good agreement with the latest Planck measurements, allowing for a wide range of acceptable values for certain parameters.