Inflation from a generalized exponential plateau: towards extra suppressed tensor-to-scalar ratios

TL;DR

This paper proposes a new inflationary potential with a flatter plateau and steeper minimum, leading to significantly suppressed tensor-to-scalar ratios below 10^{-5}, aligning with observational constraints.

Contribution

It introduces a three-parameter inflationary potential with generalized plateau features that results in extra small tensor-to-scalar ratios, extending the Starobinsky model.

Findings

Achieves tensor-to-scalar ratio r < 10^{-5}

Ensures prolonged slow-roll inflation and successful exit

Links the potential to higher-order Starobinsky corrections

Abstract

We investigate a standard minimally-coupled scalar-field inflationary scenario, which is based on a new potential, with suitably generalized plateau features, that leads to extra small tensor-to-scalar ratios. In particular, we consider a specific three-parameter potential, which has a flatter plateau and a steeper well compared to the Starobinsky potential in the Einstein frame. We study the inflationary realization and we show that it guarantees a prolonged period of slow-roll inflation and a successful exit. Additionally, the steeper minimum leads to significantly suppressed tensor perturbations, and thus to an extra-small tensor-to-scalar ratio $r$, and we show that we are able to obtain $r$ values less than $10^{-5}$. Moreover, we calculate the reheating temperature showing that in order to be in agreement with observations one of the potential parameters should remain within specific bounds. Finally, performing an inverse conformal transformation to the Jordan frame we show that the considered potential corresponds to higher-order corrections to Starobinsky potential in the Einstein frame, and these corrections are the reason for the improved behavior of the tensor-to-scalar ratio.