  Radiative heat-transport mediated by near-field interactions is known to be
superdiffusive in dilute, many-body systems. In this Letter we use a
generalized Landauer theory of radiative heat transfer in many-body planar
systems to demonstrate a nonmonotonic transition from superdiffusive to
ballistic transport in dense systems. We show that such a transition is
associated to a change of the polarization of dominant modes, leading to
dramatically different thermal relaxation dynamics spanning over three orders
of magnitude. This result could have important consequences on thermal
management at nanoscale of many-body systems.
