Universal Defect Dynamics in Two-Dimensional Convective Roll Patterns

Abstract

The process of annihilation of two point defects with opposite topological charges in a roll pattern is discussed for electrohydrodynamic convection in a nematic layer. It is shown that at the final stage of the process the distance between the centers of defects which are being annihilated varies as the square root of the time, down-counted from the annihilation moment. Such a scaling is associated with topological properties of the slowly varying complex amplitude of the order parameter and is suggested as a generic law for annihilation or spontaneous, barrierless nucleation of pairs of defects in extended systems. Experimental evidence of the scaling in the case of electrohydrodynamic convection in MBBA is obtained.