DOMAIN-STRUCTURES IN 4TH-ORDER PHASE AND GINZBURG-LANDAU EQUATIONS

In pattern-forming systems, competition between patterns with differen t wave numbers can lead to domain structures, which consist of regions with differing wave numbers separated by domain walls. For domain str uctures well above threshold we employ the appropriate phase equation and obtain detailed qualitative agreement with recent experiments. Clo se to threshold a fourth-order Ginzburg-Landau equation is used which describes a steady bifurcation in systems with two competing critical wave numbers. The existence and stability regime of domain structures is found to be very intricate due to interactions with other modes. In contrast to the phase equation the Ginzburg-Landau equation allows a spatially oscillatory interaction of the domain walls. Thus, close to threshold domain structures need not undergo the coarsening dynamics f ound in the phase equation far above threshold, and can be stable even without phase conservation. We study their regime of stability as a f unction of their (quantized) length. Domain structures are related to zig-zags in two-dimensional systems. The latter are therefore expected to be stable only when quenched for enough beyond the zig-zag instabi lity.