Key points are not available for this paper at this time.
The effect of including a Gauss-Bonnet contribution in the bulk action is investigated within the context of the steep inflationary scenario. When inflation is driven by an exponential inflaton field, this Gauss-Bonnet term allows the spectral index of the scalar perturbation spectrum to take values in the range 0.944 and 0.989, thereby bringing the scenario in closer agreement with the most recent observations. Once the perturbation spectrum is normalized to the microwave background temperature anisotropies, the value of the spectral index is determined by the Gauss-Bonnet coupling parameter and the tension of the brane and is independent of the logarithmic slope of the potential.
Lidsey et al. (Thu,) studied this question.