Beyond Starobinsky inflation

TL;DR

This paper explores a supergravity-based extension of $R+R^2$ gravity with a Born-Infeld structure, analyzing its implications for Starobinsky inflation and the behavior of the $F(R)$ function beyond the inflationary scale.

Contribution

It introduces a novel supergravity model with a Born-Infeld structure that extends $F(R)$ gravity beyond inflation, revealing differences from standard models and breaking the usual $F(R)$-scalar-tensor correspondence.

Findings

The model describes Starobinsky inflation within a supergravity framework.

It allows extrapolation of the $F(R)$ function beyond the inflationary scale.

Differences from standard $(R+R^2)$ gravity and broken $F(R)$-scalar-tensor correspondence are observed.

Abstract

A supergravity extension of the $(R+R^2)$ gravity with the additional (Born-Infeld) structure of a massive vector multiplet gives rise to the specific $F(R)$ gravity, whose structure is investigated in detail. The massive vector multiplet has inflaton (scalaron), goldstino and a massive vector field as its field components. The model describes Starobinsky inflation and allows us to extrapolate the $F(R)$ function beyond the inflationary scale (up to Planck scale). We observe some differences versus the $(R+R^2)$ gravity, and several breaking patterns of the well known correspondence between the $F(R)$ gravity and the scalar-tensor gravity.