Inflation driven by Einstein-Gauss-Bonnet gravity

TL;DR

This paper demonstrates that scalar coupled Gauss-Bonnet gravity can independently drive inflation in the early universe without slow roll approximation, transitioning smoothly to Einstein gravity post-inflation, and remains compatible with observations.

Contribution

It shows that scalar coupled Gauss-Bonnet gravity alone can cause inflation without slow roll, and addresses stability issues with a self-interacting potential.

Findings

Gauss-Bonnet term drives inflation without slow roll.

Inflationary scenario remains compatible with observations.

Transition to Einstein gravity occurs smoothly after inflation.

Abstract

We have explicitly demonstrated that scalar coupled Gauss-Bonnet gravity in four dimension can have non-trivial effects on the early inflationary stage of our universe. In particular, we have shown that the scalar coupled Gauss-Bonnet term alone is capable of driving the inflationary stages of the universe without incorporating slow roll approximation, while remaining compatible with the current observations. Subsequently, to avoid the instability of the tensor perturbation modes we have introduced a self-interacting potential for the inflaton field and have shown that in this context as well it is possible to have inflationary scenario. Moreover it turns out that presence of the Gauss-Bonnet term is incompatible with the slow roll approximation and hence one must work with the field equations in the most general context. Finally, we have shown that the scalar coupled Gauss-Bonnet term attains smaller and smaller values as the universe exits from inflation. Thus at the end of the inflation the universe makes a smooth transition to Einstein gravity.