A molecular dynamics "Maxwell Demon" experiment for granular mixtures
  We report a series of molecular dynamics simulations and investigate the possibility to separate a granular mixture of inelastic hard spheres by vigorously shaking it in a box made of two connected compartments. As its one-component counterpart, the system exhibits a ``left-right'' symmetry breaking entirely due to the inelasticity of grain-grain collisions, and triggered by increasing the number of particles. In the compartment where the density of grains is larger, we observe a partial segregation with a predominance of heavy particles. However, this compartment still has a higher density of light particles than the other one, which is light-rich. The density, granular temperature and anisotropic pressure profiles are monitored. We also discuss how to construct a relevant order parameter for this transition and show that the resulting bifurcation diagram is dominated by large fluctuations. 
A. Barrat and E. Trizac