Spurious fragmentation in filaments

Starting from 64^3 grid pre-initial data.
Starting from 64^3 Poisson pre-initial data.
Starting from 64^3 grid + 64^3 small Poisson perturbation.
Starting from 64^3 Poisson pre-initial data, but with the long-range force only. Obviously, this is unphysical but note that the regular fragmentation has disappeared.