Dynamic front transitions and spiral-vortex nucleation.

This is a study of front dynamics in reaction diffusion systems near nonequilibrium Ising-Bloch bifurcations. We find that the relation between front velocity and perturbative factors, such as external fields and curvature, is typically multivalued. This unusual form allows small perturbations to induce dynamic transitions between counterpropagating fronts and to nucleate spiral vortices. We use these findings to propose explanations for a few numerical and experimental observations, including spiral breakup driven by advective fields, and spot splitting.