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arXiv 2007.14685cond-mat.stat-mech
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具有任意相互作用势的一维均匀长程相互作用系统的动力学理论

Kinetic theory of one-dimensional homogeneous long-range interacting systems with an arbitrary potential of interaction

Jean-Baptiste Fouvry, Pierre-Henri Chavanis, Christophe Pichon

摘要:

有限$N$效应必然驱动长程相互作用$N$ -体系统的长期演化。Balescu-Lenard动力学方程一般地描述了源自${1/N}$效应的这个过程,但是对于一维均质系统,这个动力学算子由于对称性而精确地消失:这样的系统经历动力学阻塞,并且不能在${1/N}$中以这个顺序作为整体松弛。因此,只有通过更弱的${1/N^{2}}$效应(来源于三体相关性),这些系统才能放松,导致更慢的进化。在极限的集体效应可以忽略不计,但对于任意的成对相互作用潜力,我们推导出一个封闭的和明确的动力学方程描述这个非常长期的演变。我们展示了这个动力学方程如何满足一个$H$ -定理,同时保存粒子数和能量,确保不可避免的放松系统的玻尔兹曼平衡分布。假设相互作用是长程的,我们还展示了这个方程如何不会受到进一步的动力学阻塞,即,${1/N^{2}}$动力学总是有效的。最后,我们说明了这个方程如何定量匹配直接$N$体模拟测量。

英文摘要:

Finite-$N$ effects unavoidably drive the long-term evolution of long-range interacting $N$-body systems. The Balescu-Lenard kinetic equation generically describes this process sourced by ${1/N}$ effects but this kinetic operator exactly vanishes by symmetry for one-dimensional homogeneous systems: such systems undergo a kinetic blocking and cannot relax as a whole at this order in ${1/N}$. It is therefore only through the much weaker ${1/N^{2}}$ effects, sourced by three-body correlations, that these systems can relax, leading to a much slower evolution. In the limit where collective effects can be neglected, but for an arbitrary pairwise interaction potential, we derive a closed and explicit kinetic equation describing this very long-term evolution. We show how this kinetic equation satisfies an $H$-theorem while conserving particle number and energy, ensuring the unavoidable relaxation of the system towards the Boltzmann equilibrium distribution. Provided that the interaction is long-range, we also show how this equation cannot suffer from further kinetic blocking, i.e., the ${1/N^{2}}$ dynamics is always effective. Finally, we illustrate how this equation quantitatively matches measurements from direct $N$-body simulations.

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