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