Extended interactions in the Palatini-$R^2$ inflation

Understand

The Palatini formulation of the Starobinsky model does not yield a propagating scalaron that can assume the role of the inflaton field as in the conventional metric formulation.

• In the so-called Palatini-${R}^2$ models this role is assumed by a fundamental scalar field nonminimally coupled to gravity.
• In this article we consider an extension of the interactions of this field by introducing a field dependence to the $R^2$ coefficient in the form of logarithmic corrections.
• We examine the resulting predictions of the inflationary observables in the framework of slow-roll approximation and investigate the possible implications of the reheating process on these predictions.