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

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