Friction selection in nonlinear particle arrays

When a discrete nonlinear array is driven across a periodic surface spatial ly coherent modes of motion can coexist associated with different average v elocities due to resonant parametric forcing of the particle fluctuations b y the center of mass motion. Depending on the coupling strength kappa and s ize of the array N, jumps in the minimum friction (maximum velocity) exhibi ted by the array occur at kappa(m)(N) similar to (N/m)(2) as new modes stab ilize and are selected by the dynamics. The existence of such coherent mode s allows both an effective low dimensional description of the dynamics to e xist and the possibility for control of friction close to these instabiliti es.