  We study stochastic particle systems with stationary product measures that
exhibit a condensation transition due to particle interactions or spatial
inhomogeneities. We review previous work on the stationary behaviour and put it
in the context of the equivalence of ensembles, providing a general
characterization of the condensation transition for homogeneous and
inhomogeneous systems in the thermodynamic limit. This leads to strengthened
results on weak convergence for subcritical systems, and establishes the
equivalence of ensembles for spatially inhomogeneous systems under very general
conditions, extending previous results which were focused on attractive and
finite systems. We use relative entropy techniques which provide simple proofs,
making use of general versions of local limit theorems for independent random
variables.
