  We present a clear N-body realization of the growth of a Bahcall-Wolf f ~
E^0.25 (rho ~ 1/r^1.75) density cusp around a massive object ("black hole") at
the center of a stellar system. Our N-body algorithm incorporates a novel
implementation of Mikkola-Aarseth chain regularization to handle close
interactions between star and black hole particles. Forces outside the chain
were integrated on a GRAPE-6A/8 special-purpose computer with particle numbers
up to N=0.25 x 10^6. We compare our N-body results with predictions of the
isotropic Fokker-Planck equation and verify that the time dependence of the
density (both configuration and phase-space) predicted by the Fokker-Planck
equation is well reproduced by the N-body algorithm, for various choices of N
and of the black hole mass. Our results demonstrate the feasibility of
direct-force integration techniques for simulating the evolution of galactic
nuclei on relaxation time scales.
