Constraints in the context of induced-gravity inflation.

Constraints on the required flatness of the scalar potential V (�) for a cousin-model to extended inflation are studied. It is shown that, unlike earlier results, Induced-gravity Inflation can lead to successful inflation with a very simple lagrangian and � ∼ 10 −6 , rather than 10 −15 as previously reported. A second order phase transition further enables this model to escape the ‘big bubble’ problem of extended inflation, while retaining the latter’s motivations based on the low-energy effective lagrangians of supergravity, superstring, and Kaluza-Klein theories.