A simple $F(\mathcal{R},\varphi )$ deformation of Starobinsky inflationary model

Abstract

We study a model including a real scalar field $\varphi$ non-minimally coupled to $F(\mathcal{R})$ 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 $\varphi$ in the $F(\mathcal{R})$-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.

22 pages, 13 figures, text modified and references added, matches the published version