Defects in Oscillatory Media: Toward a Classification

We investigate, in a systematic fashion, coherent structures, or defects, which serve as inter- faces between wave trains with possibly dierent,wavenumbers in reaction-diusion,systems. We propose a classification of defects into four dierent,defect classes which have all been observed experimentally. The characteristic distinguishing these classes is the sign of the group velocities of the wave trains to either side of the defect, measured relative to the speed of the defect. Using a spatial-dynamics description in which defects correspond to homoclinic and heteroclinic connections of an ill-posed pseudo-elliptic equation, we then relate robustness properties of de- fects to their spectral stability properties. Lastly, we illustrate that all four types of defects occur in the one-dimensional cubic-quintic Ginzburg‐Landau equation as a perturbation of the phase-slip vortex. 1 Contents