Resonant and non-resonant relaxation of globular clusters

ABSTRACT Globular clusters contain a finite number of stars. As result, they inevitably undergo secular evolution (‘relaxation’) causing their mean distribution function (DF) to evolve on long time-scales. On one hand, this long-term may be interpreted as driven by the accumulation local deflections along each star’s field trajectory – so-called ‘non-resonant relaxation’ (NR). other it can thought non-local, collectively dressed, and resonant couplings between stellar orbits, process termed ‘resonant (RR). In paper, we consider model globular cluster represented spherical, isotropic isochrone DF, compare in detail predictions both RR NR theories against tailored direct N-body simulations. space orbital actions (namely radial action total angular momentum), find that predict correct morphology for cluster’s although theory overestimates amplitude relaxation rate factor ∼2. We conclude hot spherical is not dominated amplified large-scale potential fluctuations, despite existence strong ℓ = 1 damped mode. Instead, collective amplification affects only marginally even largest scales. The predicted contributions from smaller scale fluctuations are essentially same theories.