  We present molecular dynamics simulations of aggregation kinetics in a
colloidal suspension modeled as a highly asymmetric binary mixture. Starting
from a configuration with largely uncorrelated colloidal particles the system
relaxes by coagulation-fragmentation dynamics to a structured state of
low-dimensionality clusters with an exponential size distribution. The results
show that short-range repulsive interactions alone can give rise to so-called
cluster phases. For the present model and probably other, more common colloids,
the observed clusters appear to be equilibrium phase fluctuations induced by
the entropic inter-colloidal attractions.
