In this Letter we study subcritical transitions in spatially extended systems when topological defects are present. The behavior of a single defect is discussed in the framework of Ginzburg-Landau models. We show how the transition from one stable state to the other is affected by the presence of defects. Our results, claimed to be independent of these models, are illustrated with examples coming from Couette-Taylor, liquid crystals and convective instabilities.

• Received 12 December 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.2957