Formation of vortices by the RWI (fiducial case). From left to right: evolution of the density in the (r,θ) plane at t = 0, t = 30, and t = 190 rotations. The density is relative to the disk, σ/σ₀(r)−1, and shows the formation of a chain of six vortices, in agreement with the m = 6 most unstable azimuthal mode. After fewer than 200 rotations, the chain merges in a single vortex. The aspect ratio of the vortices is of the order of 5.2 at t = 30 rotations and 7.4 at t = 190 rotations.