  The suggestion that there exist causally disconnected universes or
sub-universes to explain the values of physical parameters such as the
cosmological constant is discussed. A statistical model of the string
landscape/topography is formulated using a stochastic Langevin equation for
string and supergravity potentials. A Focker-Planck equation for the
probability density of superpotentials is derived and the possible
non-supersymmetric multivacua describing string/M-theory topography are
investigated. The stochastic fluctuations of the superpotentials and their
associated vacuum states can possibly lead to a small positive cosmological
constant.
