Stochastic String Topography and Multivacua
  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. 
J. W. Moffat