  Domain walls between spatially periodic patterns with different wave numbers,
can arise in pattern-forming systems with a neutral curve that has a double
minimum. Within the framework of the phase equation, the interaction of such
walls is purely attractive. Thus, they annihilate each other and, if the total
phase is not conserved, the final state will be periodic with a single wave
number. Here we study the stability of arrays of domain walls (domain
structures) in a fourth-order Ginzburg-Landau equation. We find a discrete set
of domain structures which differ in the quantized lengths of the domains. They
are stable even without phase conservation, as, for instance, in the presence
of a subcritical ramp in the control parameter. We attribute this to the
spatially oscillatory behavior of the wave number which should lead to an
oscillatory interaction between the domain walls. These results are expected to
shed also some light on the stability of two-dimensional zig-zag structures.
