We consider a model in which the Universe is the direct product of an ordin
ary (3 + 1)-dimensional space-a brane where all the standard model fields a
re confined-and a compact hyperbolic manifold. The decay of massive Kaluza-
Klein modes leads to the injection of bulk entropy into the observable Univ
erse. The large statistical averaging inherent in the collapse of the initi
al entropy onto the brane smoothes out any initial inhomogeneities in the d
istribution of matter and of three-curvature.