Cosmological inflation in F(R,G) gravity

Cosmological inflation is discussed in the framework of F(R,G) gravity where F is a generic function of the curvature scalar R and the Gauss-Bonnet topological invariant G. The main feature that emerges in this analysis is the fact that this kind of theory can exhaust all the curvature budget related to curvature invariants without considering derivatives of R, R-mu v, R-sigma mu v(lambda), etc., in the action. Cosmological dynamics results driven by two effective masses (lengths) are related to the R scalaron and the G scalaron working respectively at early and very early epochs of cosmic evolution. In this sense, a double inflationary scenario naturally emerges.