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Colloquium
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Small traveling clusters in attractive and in repulsive HMF models 山口 義幸 4月17日(金) 13時00分
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. |
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