Inflationary cosmology based on Weyl-scaled induced gravity

It is shown that successful extended inflation can occur in (Weyl-scaled) minimal theories of gravity, such as a certain superstring theory, Kaluza-Klein theory, $N$-dimensional gravity, ${\mathcal{R}}^2$ gravity, and induced-gravity models. In these models, during the matter-dominated epoch, time-varying inertia of cosmic matter acts as an effective dark matter. Therefore, the present density parameter of visible matter is ${\Omega }_{\sigma }<1\mathrm{}$, even if the Universe is geometrically flat ($k=0\mathrm{}$).