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arXiv · 2005.03202

Classical Goldstone modes in Long-Range Interacting Systems

Tarcisio M Rocha Filho·Bruno Marcos
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Abstract

For a classical system with long-range interactions, a soft mode exists whenever a stationary state spontaneously breaks a continuous symmetry of the Hamiltonian. Besides that, if the corresponding coordinate associated to the symmetry breaking is periodic, the same energy of the different stationary states and finite $N$ thermal fluctuations result in a superdiffusive motion of the center of mass for total zero momentum, that tends to a normal diffusion for very long-times. As examples of this, we provide a two-dimensional self-gravitating system, a free electron laser and the Hamiltonian Mean-Field (HMF) model. For the latter, a detailed theory for the motion of the center of mass is given. We also discuss how the coupling of the soft mode to the mean-field motion of individual particles may lead to strong chaotic behavior for a finite particle number, as illustrated by the HMF model.

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Tarcisio M Rocha Filho, Bruno Marcos. 2020-05-07. Classical Goldstone modes in Long-Range Interacting Systems. https://doi.org/10.1103/physreve.102.032122

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