  Three colloidal spheres driven around a ring-like optical trap known as an
optical vortex have been predicted to undergo periodic collective motion due to
their hydrodynamic coupling. In fact, the quenched disorder in the
optically-implemented potential energy landscape drives a transition to
instability evolving into microscopic weak chaos with fractional dynamics. As a
result, the relation between the space-time selfsimilarity of the system's
collective transport properties and its microscopic weak chaos dynamics is
revealed.
