Cosmology and hierarchy in stabilized warped brane models

We examine the cosmology and hierarchy of scales in models with branes imme rsed in a five-dimensional curved spacetime subject to radion stabilization . When the radion field is time-independent and the inter-brane spacing is stabilized, the universe can naturally find itself in the radiation-dominat ed epoch. This feature is independent of the form of the stabilizing potent ial. We recover the standard Friedmann equations without assuming a specifi c form for the bulk energy-momentum tensor. In the models considered, if th e observable brane has positive tension, a solution to the hierarchy proble m requires the presence of a negative tension brane somewhere in the bulk. We find that the string scale can be as low as the electroweak scale. In th e situation of self-tuning branes where the bulk cosmological constant is s et to zero, the brane tensions have hierarchical values. In the case of a p olynomial stabilizing potential no new hierarchy is created. (C) 2000 Publi shed by Elsevier Science B.V.