title: Small traveling clusters in attractive and repulsive Hamiltonian mean-field models.
abstract: Long-lasting small traveling clusters are studied in the Hamiltonian mean-field model by comparing between attractive and repulsive interactions. Nonlinear Landau damping theory predicts that a Gaussian momentum distribution on a spatially homogeneous background permits the existence of traveling clusters in the repulsive case, as in plasma systems, but not in the attractive case. Nevertheless, extending the analysis to a two-parameter family of momentum distributions of Fermi-Dirac type, we theoretically predict the existence of traveling clusters in the attractive case; these findings are confirmed by direct N -body numerical simulations. The parameter region with the traveling clusters is much reduced in the attractive case with respect to the repulsive case.
authors.affiliation: Laboratoire J. A. Dieudonné, Université de Nice Sophia-Antipolis, UMR CNRS 6621, Parc Valrose, F-06108 Nice Cedex 02, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Barré
authors.forename: Yoshiyuki Y
authors.initials: YY
authors.lastname: Yamaguchi