String inspired braneworld cosmology

TL;DR

It is shown that variation in the bulk geometry is produced by bulk curvature terms parametrized by the mass of a black hole, and there is a coupling between these curvature Terms and matter that can be relevant for early universe cosmology.

Abstract

We consider braneworld scenarios including the leading correction to the Einstein-Hilbert action suggested by superstring theory, the Gauss-Bonnet term. We obtain and study the complete set of equations governing the cosmological dynamics. We find they have the same form as those in Randall-Sundrum scenarios but with time-varying four-dimensional gravitational and cosmological constants. Studying the bulk geometry we show that this variation is produced by bulk curvature terms parameterized by the mass of a black hole. Finally, we show there is a coupling between these curvature terms and matter that can be relevant for early universe cosmology.

Figures (1)

• Figure 1: Variation of the effective 4D gravitational and cosmological constants, $\tilde{\kappa}^2_\ast$ and $\tilde{\Lambda}_\ast$, with respect to the scale factor $a_o$ [Eq. (\ref{['fdef']})]. (a) $\tilde{\Lambda}_\ast$ has a minimum. (b) $\tilde{\Lambda}_\ast$ is a monotonic function of $a_o$.