  We present the results from realistic N-body modelling of massive star
clusters in the Magellanic Clouds. We have computed eight simulations with N ~
10^5 particles; six of these were evolved for at least a Hubble time. The aim
of this modelling is to examine the possibility of large-scale core expansion
in massive star clusters and search for a viable dynamical origin for the
radius-age trend observed for such objects in the Magellanic Clouds. We
identify two physical processes which can lead to significant and prolonged
cluster core expansion: mass-loss due to rapid stellar evolution in a
primordially mass segregated cluster, and heating due to a retained population
of stellar-mass black holes. These two processes operate over different
time-scales - the former occurs only at early times and cannot drive core
expansion for longer than a few hundred Myr, while the latter typically does
not begin until several hundred Myr have passed but can result in core
expansion lasting for many Gyr. We investigate the behaviour of these expansion
mechanisms in clusters with varying degrees of primordial mass segregation and
in clusters with varying black hole retention fractions. In combination, the
two processes can lead to a wide variety of evolutionary paths on the
radius-age plane, which fully cover the observed cluster distribution and hence
define a dynamical origin for the radius-age trend in the Magellanic Clouds. We
discuss the implications of core expansion for various aspects of globular
cluster research, as well as the possibility of observationally inferring the
presence of a population of stellar-mass black holes in a cluster.
