Three unequal masses on a ring and soft triangular billiards
  The dynamics of three soft interacting particles on a ring is shown to correspond to the motion of one particle inside a soft triangular billiard. The dynamics inside the soft billiard depends only on the {\it masses ratio} between particles and {\it softness ratio} of the particles interaction. The transition from soft to hard interaction can be appropriately explored using potentials for which the corresponding equations of motion are well defined in the hard wall limit. Numerical examples are shown for the soft Toda-like interaction and the error function. 
H. A. Oliveira and G. A. Emidio and M. W. Beims
nlin.CD