Speaker
Description
Starobinsky's $R+\alpha R^2$ model provides a compelling description of cosmic inflation, and its observational support has established it as a benchmark for model comparison. However, at the same order in the local curvature expansion, an effective theory of spacetime geometry naturally includes the Weyl-squared invariant $W^2$, making $R+\alpha R^2−\beta W^2$ the minimal purely gravitational theory of inflation at quadratic order. In this talk I present the inflationary predictions of this theory, adopting a self-consistent approach that avoids spurious degrees of freedom typically arising in higher-curvature gravity. We compute primordial observables in the Jordan frame up to next-to-next-to-next-to-leading order (N3LO) in the slow-roll expansion, providing high-precision predictions for upcoming CMB observations.