  Many-body long-range interacting systems can remain approximately in a
quasi-stationary state far-from-thermodynamic equilibrium. These states are
typically characterized by a pair of counter-propagating density clusters, or
by a single non-homogeneous core-halo in the phase-space of the particles. By
using particle simulations based on the Hamiltonian mean-field model, we show
that this model supports stationary states with multiple cluster or particle
holes in phase-space density. We also propose a mechanism based on wave-wave
and wave-particle interactions that lead to the formation of these clusters,
and characterize these new quasi-stationary states in terms of the initial
parameters of the simulations.
