Spontaneous spirals in vibrated granular chains,
R.E. Ecke, Z.A. Daya, M.K. Rivera, and E. Ben-Naim
We present experimental measurements on the spontaneous formation of
compact spiral structures in vertically-vibrated granular
chains. Under weak vibration, when the chain is quasi two-dimensional
and self-avoiding, spiral structures emerge from generic initial
configurations. We compare geometrical characteristics of the spiral
with that of an ideal tight spiral. Globally, the spiral undergoes a
slow rotation such that to keep itself wound, while internally, fast
vibrational modes are excited along the backbone with transverse
oscillations dominating over longitudinal ones. Spirals have an
extremely small volume in phase space, and hence, their formation
demonstrates how nonequilibrium dynamics can result in a nonuniform
sampling of phase space.
src,
ps,
pdf