  Zero-range processes with decreasing jump rates are well known to exhibit a
condensation transition under certain conditions on the jump rates, and the
dynamics of this transition continues to be a subject of current research
interest. Starting from homogeneous initial conditions, the time evolution of
the condensed phase exhibits an interesting coarsening phenomenon of mass
transport between cluster sites characterized by a power law. We revisit the
approach in [C. Godreche, J. Phys. A: Math. Gen., 36(23) 6313 (2003)] to derive
effective single site dynamics which form a non-linear birth death chain
describing the coarsening behaviour. We extend these results to a larger class
of parameter values, and introduce a size-biased version of the single site
process, which provides an effective tool to analyze the dynamics of the
condensed phase without finite size effects and is the main novelty of this
paper. Our results are based on a few heuristic assumptions and exact
computations, and are corroborated by detailed simulation data.
