Multiscale energy spreading in hard-particle chains

We consider a one-dimensional array of particles interacting via an infinite well potential. We explore the properties of energy spreading from an initial state where only a group of particles has nonzero velocities, while others are at rest. We characterize anomalous diffusion of the active domain via moments and entropies of the energy distribution. Only in the special cases of a single-well potential (hard-particle gas) and when the distance between particles is half the potential width, does diffusion exhibit a single scale; otherwise, multiscale anomalous diffusion is observed.