PATTERN-FORMATION FROM DEFECT CHAOS - A THEORY OF CHEVRONS

For over 25 years it is known that the roll structure of electroconvec tion (EC) in the dielectric regime in planarly aligned nematic liquid crystals has, after a transition to defect chaos, the tendency to form chevron structures. We show, with the help of a coarse-grained model, that this effect can generally be expected for systems with spontaneo usly broken isotropy, that is lifted by a small external perturbation. The linearized model as well as a nonlinear extension are compared to simulations of a system of coupled amplitude equations which generate chevrons out of defect chaos. The mechanism of chevron formation is s imilar to the development of Turing patterns in reaction-diffusion sys tems. Copyright (C) 1998 Elsevier Science B.V.