Dynamic Scaling of Coupled Nonequilibrium Interfaces
  We propose a simple discrete model to study the nonequilibrium fluctuations of two locally coupled 1+1 dimensional systems (interfaces). Measuring numerically the tilt-dependent velocity we construct a set of stochastic continuum equations describing the fluctuations in the model   The scaling predicted by the equations are studied analytically using dynamic renormalization group and compared with simulation results. When the coupling is symmetric, the well known KPZ exponents are recovered. If one of the systems is fluctuating independently, an increase in the roughness exponent is observed for the other one. 
Albert-L\'aszl\'o Barab\'asi