Rotational Brownian motion (astronomy) supermassive black holes at the centers of galaxies. Perturbations from passing stars can alter the orbital plane of such a binary, which in turn alters the direction of the spin axis of the single black hole that forms when the two coalesce. Rotational Brownian motion is often observed in N-body simulations of galaxies containing binary black holes. The massive binary sinks to the center of the galaxy via dynamical friction where it interacts with passing stars. The same gravitational perturbations that induce a random walk in the orientation of the binary, also cause the binary to shrink, via the gravitational
Brownian surface Brownian surface A Brownian surface is a fractal surface generated via a fractal elevation function. For instance, in the three-dimensional case, where two variables "X" and "Y" are given as coordinates, the elevation function between any two points ("x", "y") and ("x", "y") can be set to have a mean or expected value that increases as the vector distance between ("x", "y") and ("x", "y"). There are, however, many ways of defining the elevation function. For instance, the fractional Brownian motion variable may be used, or various rotation functions may be used to achieve more natural looking surfaces. As with