Brane inflation and the robustness of the Starobinsky inflationary model

TL;DR

This paper tests the robustness of the Starobinsky inflation model by extending it with a parameter motivated by brane inflation and finds it remains consistent with current cosmological data.

Contribution

It introduces a generalized $eta$-Starobinsky inflation model and constrains its deviation from the original model using observational data.

Findings

Only a small deviation from the original model is allowed ($eta=-0.08 \u00b1 0.12$).

The results confirm the robustness of the Starobinsky inflationary model.

Current data fully supports the original model's predictions.

Abstract

The first inflationary model conceived was the one proposed by Starobinsky which includes an additional term quadratic in the Ricci-scalar R in the Einstein-Hilbert action. The model is now considered a target for several future cosmic microwave background experiments given its compatibility with current observational data. In this paper, we analyse the robustness of the Starobinsky inflation by inserting it into a generalized scenario based on a $\beta$-Starobinsky inflation potential, which is motivated through brane inflation. In the Einstein frame, the generalized model recovers the original model for $\beta=0$, whereas $\forall \beta \neq 0$ represents an extended class of models that admit a wider range of solutions. We investigate limits on $\beta$ from current cosmic microwave background and baryonic acoustic oscillation data and find that only a small deviation from the original scenario is allowed, $\beta=-0.08 \pm 0.12$ (68% C.L.), which is fully compatible with zero and confirms the robustness of the Starobinsky inflationary model in light of current observations.