Kinetic theory of one-dimensional inhomogeneous long-range interacting $N$-body systems at order $1/N^2$ without collective effects

Abstract

Long-range interacting systems irreversibly relax as a result of their finite number of particles, $N$. At order $1/N$, this process is described by the inhomogeneous Balescu--Lenard equation. Yet, this equation exactly vanishes in one-dimensional inhomogeneous systems with a monotonic frequency profile and sustaining only 1:1 resonances. In the limit where collective effects can be neglected, we derive a closed and explicit $1/N^2$ collision operator for such systems. We detail its properties highlighting in particular how it satisfies an $H$-theorem for Boltzmann entropy. We also compare its predictions with direct $N$-body simulations. Finally, we exhibit a generic class of long-range interaction potentials for which this $1/N^2$ collision operator exactly vanishes.

9 pages, 1 figure, submitted to APS

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• A numerical study of vector resonant relaxation
• Kinetic theory of one-dimensional homogeneous long-range interacting systems with an arbitrary potential of interaction
• Secular Dynamics around a Supermassive Black Hole via Multipole Expansion