  We review some theories of non-equilibrium Bose-Einstein condensates in
potentials, in particular of the Bose-Einstein condensate of polaritons. We
discuss such condensates, which are steady-states established through a balance
of gain and loss, in the complementary limits of a double-well potential and a
random disorder potential. For equilibrium condensates, the former corresponds
to a Josephson junction, whereas the latter is the setting for the
superfluid/Bose glass transition. We explore the non-equilibrium generalization
of these phenomena, and highlight connections with mode selection and
synchronization.
