  Several different kinds of criteria for non-equilibrium phase separation to
discriminate the two stages, the spinnodal decompostion (SD) and domain growth
(DG), are compared and further investigated. The characteristic domain size and
morphological function present two geometric criteria. Both of them can only
provide rough estimations for the crossover from SD to DG. The reason for
domain size is that the crossover in this description covers a process, instead
of a specific time. The reason for the morphological function is that the
result may rely on chosen threshold value. However, both the non-equilibrium
strength and the entropy production rate are physical criteria and are more
convenient to provide critical times. In fact, not only the non-equilibrium
strength defined in the moment space opened by all the independent components
of the used non-equilibrium quantities but also those defined in its subspaces
can be used as criteria. Each of those criteria characterizes the phase
separation process from its own perspective. Consequently, the obtained
critical times may show slight differences. It should be pointed out that these
slight differences are not contradictive, but consistent with each other and
complementary in describing the complex phenomena.
