  According to a model of quantum cosmology the maximum number of degrees of
freedom allowed in our three dimensions was determined by the size of seven
extra dimensions in an initial excited state before inflation. The size of the
extra dimensions can be inferred from a simple scheme for unifying the strong
force and gravity. Coupled with the Bekenstein-Hawking entropy bound, these
considerations lead to a scaling law for the cosmological constant that has
been proposed independently by several authors.
