  Fluctuation-dominated phase ordering refers to a steady state in which the
magnitude of long-range order varies strongly owing to fluctuations, and to the
associated coarsening phenomena during the approach to steady state. Strong
fluctuations can lead to a number of interesting phenomena, including a cusp
singularity in the scaled correlation function, implying the breakdown of the
Porod Law. First identified in a nonequilibrium system of passively sliding
particles on a fluctuating surface, fluctuation-dominated order also occurs in
several other systems, including an equilibrium Ising model with long-range
interactions. This article discusses these systems, and others where clustering
effects are stronger.
