  We investigate equilibration processes shortly after sudden perturbations are
applied to ultracold trapped superfluids. We show the similarity of phase
imprinting and localized density depletion perturbations, both of which
initially are found to produce "phase walls". These planar defects are
associated with a sharp gradient in the phase. Importantly they relax following
a quite general sequence. Our studies, based on simulations of the complex
time-dependent Ginzburg-Landau equation, address the challenge posed by these
experiments: how a superfluid eventually eliminates a spatially extended planar
defect. The processes involved are necessarily more complex than equilibration
involving simpler line vortices. An essential mechanism for relaxation involves
repeated formation and loss of vortex rings near the trap edge.
