Relaxation of hierarchy in higher-dimensional Starobinsky model

TL;DR

This paper shows that higher-dimensional extensions of the Starobinsky inflation model are less sensitive to additional curvature terms, simplifying the construction of such models in more than four dimensions.

Contribution

It demonstrates that the observational predictions of higher-dimensional Starobinsky models are more robust against higher-order curvature corrections than the original four-dimensional model.

Findings

Higher-dimensional models are less sensitive to $R^{m}$ terms.

Simplifies the development of Starobinsky-like models in extra dimensions.

Enhances robustness of inflation predictions in extended models.

Abstract

Starobinsky model, which has a Ricci scalar squared term $R^{2}$ in its action, is one of the most promising inflation models from the viewpoint of Cosmic Microwave Background observations. However, it is well known that observational predictions of this model are quite sensitive to the existence of $R^{m}$ $(2<m)$ terms, whose absence is just assumed. In this paper, we clarify that the observational predictions of $D$-dimensional ($4<D$) extended Starobinsky model are less sensitive to such terms than those of the original 4-dimensional model.This result make it easier to construct Starobinsky-like models in higher dimensions.