Radion potential and brane dynamics

We examine the cosmology of Randall-Sundrum model in a dynamic setting wher e scalar fields are present in the bulk as well as the branes. This generat es a mechanism similar to that of Goldberger-Wise for radion stabilization and the recovery of late-time cosmology features on the branes. Due to the induced radion dynamics, the inflating branes; roll towards the minimum of the radion potential, thereby exiting inflation and reheating the universe. In the slow roll part of the potential, the TeV branes have maximum inflat ion rate and energy as their coupling to the radion and bulk modes have min imum suppression. Hence, when rolling down the steep end of the potential t owards the stable point, the radion field (which appears as the inflaton of the effective 4-D theory in the branes) decays very fast and reheats the u niverse. This process results in a decrease of the brane's canonical vacuum energy, Lambda (4). However, at the minimum of the potential Lambda (4) is small but not necessarily zero and the fine-tuning issue remains. Density perturbation constraints introduce an upper bound on Lambda (4). Due to the large radion mass and strong suppression to the bulk modes, moduli problem s and bulk reheating do not occur. The reheat temperature and a sufficient number of e-folding constraints for the brane-universe are also satisfied. The model therefore recovers the radiation dominated FRW universe.