Cosmological consequences of the brane/bulk inter-action

We investigate cosmological consequences arising from the interaction betwe en a homogeneous and isotropic brane-universe and the bulk. A Friedmann equ ation is derived which incorporates both the brane and bulk matter contribu tions, which are both assumed to be of arbitrary fluid form. In particular, new terms arise which describe the energy flow onto (or away from) the bra ne, as well as changes of the equation of state in the bulk. We discuss Ran dall-Sundrum type models as well as dilatonic domain walls and carefully co nsider the conditions for stabilizing the induced gravitational constant. F urthermore, consequences for cosmological perturbations are analyzed. We sh ow that, in general, super-horizon amplitudes are not constant. (C) 2000 El sevier Science B.V. All rights reserved.