# A simple $F({\cal R},\phi)$ deformation of Starobinsky inflationary model

## TL;DR

This paper explores a modified inflationary model combining $F({
m R})$ gravity with a scalar field, resulting in two-field potentials that align with observational data, extending the Starobinsky model.

## Contribution

It introduces a new $F({
m R}, \, \phi)$ deformation of the Starobinsky model with specific scalar potentials, demonstrating viability with current observations.

## Key findings

- All three potential cases produce viable inflationary scenarios.
- The models are conformally equivalent to Einstein-Hilbert theory with two scalar fields.
- Results are consistent with current cosmological data.

## Abstract

We study a model including a real scalar field $\phi$ non-minimally coupled to $F({\cal R})$ gravity, which is conformally equivalent to an Einstein-Hilbert theory, involving two real scalar fields. We consider three special cases of the potential of the field $\phi$ in the $F({\cal R})$-frame: a vanishing potential, a mass term and a Higgs potential. All these lead to non-trivial two-field potentials in the Einstein-frame which in particular directions resemble the well-known Starobinsky model. We find, that all these cases can yield viable inflationary models in complete agreement with current observational data.