BICEP/Keck data and quadratic gravity

Abstract The recent results of the BICEP and Keck collaborations have put stringent bounds on many inflationary models, including some well-motivated ones. This is certainly case when gravity remains described by Einstein's theory up to scale, but can be avoided introducing quadratic-in-curvature terms that are effective at scale. Recently it has also been shown these UV complete respecting stability unitarity. Here predictions such quadratic computed compared with BICEP/Keck constraints focusing scenarios best-motivated from particle physics point view already ruled out in Einstein gravity: (critical) Higgs inflation natural inflation. first scenario considered as most economical option inflaton identified only known elementary scalar field Standard Model near criticality used remain perturbative regime. In second one a pseudo-Nambu-Goldstone boson contributes dynamics its potential naturally flat. It both restore agreement observational gravity.