  Granulation of quantum matter -- the formation of persistent small-scale
patterns -- is realized in the images of quasi-one-dimensional Bose-Einstein
condensates perturbed by a periodically modulated interaction. Our present
analysis of a mean-field approximation suggests that granulation is caused by
the gradual transformation of phase undulations into density undulations. This
is achieved by a suitably large modulation frequency, while for low enough
frequencies the system exhibits a quasi-adiabatic regime. We show that the
persistence of granulation is a result of the irregular evolution of the phase
of the wavefunction representing an irreversible process. Our model predictions
agree with numerical solutions of the Schr\"odinger equation and experimental
observations. The numerical computations reveal the emergent many-body
correlations behind these phenomena via the multi-configurational
time-dependent Hartree theory for bosons (MCTDHB).
