Violation of slow-roll in nonminimal inflation

We show that a nonminimal coupling to gravity can not only make some inflationary models consistent with cosmological data, similar to the case of Higgs inflation, but can also invoke slow-roll violation to realize a graceful exit from inflation. In particular, this is the case in models where a destabilizing mechanism that ends inflation should be assumed when the model is minimally coupled to gravity. As explicit examples, we consider the power-law and inverse monomial inflation models with a nonminimal coupling to gravity. While these models are excluded in the minimally coupled case, we show that they can become viable again in nonminimally coupled scenarios. In most scenario we considered, reheating can be naturally realized via gravitational particle production but this depends on the underlying theory of gravity in a nontrivial way reheating can be naturally realized via gravitational particle production but that this depends on the underlying theory of gravity in a nontrivial way.