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

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/N2 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 toward 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/N2 dynamics is always effective. Finally, we illustrate how this equation quantitatively matches measurements from direct N-body simulations.