Boundary-Induced Pattern Formation from Uniform Temporal Oscillation

Pattern dynamics triggered by fixing a boundary is investigated. By considering a reaction-diffusion equation that has a unique spatially-uniform and limit cycle attractor under a periodic or Neumann boundary condition, and then by choosing a fixed boundary condition, we found three novel phases depending on the ratio of diffusion constants of activator to inhibitor: transformation of temporally periodic oscillation into a spatially-periodic fixed pattern, travelling wave emitted from the boundary, and aperiodic spatiotemporal dynamics. The transformation into a fixed, periodic pattern is analyzed by crossing of local nullclines at each spatial point, shifted by diffusion terms. A spatial map, then, is introduced, whose temporal sequence can reproduce the spatially periodic pattern, by replacing the time with space. The generality of the boundary-induced pattern formation as well as its relevance to biological morphogenesis is discussed.