Large extra dimensions and cosmological problems - art. no. 103511

We consider a variant of the brans-world model in which the universe is the direct product of a Friedmann-Robertson-Walker (FRW) space and a compact h yperbolic manifold of dimension d greater than or equal to2. Cosmology in t his space is particularly interesting. The dynamical evolution of the space -time leads to the injection of a large entropy into the observable (FRW) u niverse. The exponential dependence of surface area on distance in hyperbol ic geometry makes this initial entropy very large, even if the CHM has a re latively small diameter (in fundamental units). The very large statistical averaging inherent in the collapse of the initial entropy onto the brane ac ts to smooth out initial inhomogeneities. This smoothing is then sufficient to account for the current homogeneity of the universe. With only mild fin e-tuning, the current flatness of the universe can also then be understood. Finally, recent brane-world approaches to the hierarchy problem can be rea dily realized within this framework.