Collisions of pulses can lead to holes via front interaction in the cubic-quintic complex Ginzburg-Landau equation in an annular geometry

We study the interaction of counterpropagating pulse solutions for two coupled complex cubic-quintic Ginzburg-Landau equations in an annular geometry. For small approach velocity we find as an outcome of such collisions several results including zigzag bound pulses, stationary bound states of 2 pi holes, zigzag 2 pi holes, stationary bound states of pi holes, zigzag bound states of pi holes, propagating 2 pi holes, and propagating pi holes as the real part of the cubic cross coupling between the counterpropagating waves is increased. We characterize in detail the collisions giving rise to the three states involving pi holes as an outcome.