For stochastic processes leading to condensation, the condensate, once it is
formed, performs an ergodic stationary-state motion over the system. We analyse
this motion, and especially its characteristic time, for zero-range processes.
The characteristic time is found to grow with the system size much faster than
the diffusive timescale, but not exponentially fast. This holds both in the
mean-field geometry and on finite-dimensional lattices. In the generic
situation where the critical mass distribution follows a power law, the
characteristic time grows as a power of the system size.Comment: 27 pages, 7 figures. Minor changes and updates performe