Gauss-Bonnet inflation

We consider an Einstein-scalar-Gauss-Bonnet gravitational theory, and argue that at early times the Ricci scalar can be safely ignored. We then demonstrate that the pure scalar-Gauss-Bonnet theory, with a quadratic coupling function, naturally supports inflationary---de Sitter---solutions. During inflation, the scalar field decays exponentially and its effective potential remains always bounded. The theory also contains solutions where these de Sitter phases possess a natural exit mechanism and are replaced by linearly expanding---Milne---phases.