Coherent behavior of balls in a vibrated box
  We report observations on very low density limit of one and two balls, vibrated in a box, showing a coherent behavior along a direction parallel to the vibration. This ball behavior causes a significant reduction of the phase space dimension of this billiard-like system. We believe this is because the lowest dissipation process along a non-ergodic orbit eliminates ball rotation and freezes transverse velocity fluctuations. From a two-ball experiment performed under low-gravity conditions, we introduce a "laser-like" ball system as a prototype of a new dynamical model for very low density granular matter at nonequilibrium steady state. 
Yves Garrabos (ICMCB), Pierre Evesque (LMSSM), Fabien Palencia   (ICMCB), Carole Lecoutre-Chabot (ICMCB), Daniel Beysens (SB...