Inflation with $f(R,\phi)$ in Jordan frame

Understand

We consider an $f(R)$ action that is non-minimally coupled to a massive scalar field.

• The model closely resembles scalar-tensor theory and by conformal transformation can be transformed to Einstein frame.
• To avoid the ambiguity of the frame dependence, we obtain an exact analytical solution in Jordan frame and show that the model leads to a period of accelerated expansion with an exit.
• Further, we compute the scalar and tensor power spectrum for the model and compare them with observations.