PHASE INSTABILITY AND DEFECT BEHAVIOR IN MODULATED WAVE PATTERNS

The application of external fields on spatio-temporal Hopf bifurcations is known to modify the stability of the associated wave patterns. In particular, left and right travelling waves are linearly coupled by pure temporal modulations provided the frequency of these modulations is close to twice the critical ones, and travelling waves may be transformed into standing waves even in regimes where the latter are otherwise unstable. The stability of such forced standing waves versus long wavelength perturbations is investigated in connection with recent experimental observations. Furthermore, we study. analytically and numerically, the dynamical behavior of the topological defects of these waves. It is shown that, in the presence of group velocity, moving dislocation pairs are formed. Hence, this system provides another example where defect motion is induced by the nonvariational character of the dynamics.