Directed Surfaces in Disordered Media
  The critical exponents for a class of one-dimensional models of interface depinning in disordered media can be calculated through a mapping onto directed percolation (DP). In higher dimensions these models give rise to directed surfaces, which do not belong to the directed percolation universality class. We formulate a scaling theory of directed surfaces, and calculate critical exponents numerically, using a cellular automaton that locates the directed surfaces without making reference to the dynamics of the underlying interface growth models. 
A.-L. Barab\'asi, G. Grinstein, and M.A. Mu\~noz (IBM, TJ Watson   Research Center)