Slow-roll inflation in Palatini $F(R)$ gravity

Understand

We study single field slow-roll inflation in the presence of $F(R)$ gravity in the Palatini formulation.

• In contrast to metric $F(R)$, when rewritten in terms of an auxiliary field and moved to the Einstein frame, Palatini $F(R)$ does not develop a new dynamical degree of freedom.
• However, it is not possible to solve analytically the constraint equation of the auxiliary field for a general $F(R)$.
• We propose a method that allows us to circumvent this issue and compute the inflationary observables.