Spotting deviations from R^2 inflation

Understand

We discuss the soundness of inflationary scenarios in theories beyond the Starobinsky model, namely a class of theories described by arbitrary functions of the Ricci scalar and the K-essence field.

• We discuss the pathologies associated with higher-order equations of motion which will be shown to constrain the stability of this class of theories.
• We provide a general framework to calculate the slow-roll parameters and the corresponding mappings to the theory parameters.
• For paradigmatic gravitational models within the class of theories under consideration we illustrate the power of the Planck/Bicep2 latest results to constrain such gravitational Lagrangians.