Evolution of the maximal particle density (top) and the horizontal gas dispersion (bottom), for 4, 16, and 32 particles per grid cell (respectively red, black, and blue curves). The initial maximal particle overdensity is reduced from ϵ/ϵ₀ = 2.4 to 1.6 and finally 1.3, when increasing the particle number by a factor of 4 each time. The lowest particle number simulation shows fastest growth. In higher particle number runs, the initial dormant phase persists longer and growth rates become lower. Results from run2.n4, run2, and run2.n64.