UNIVERSAL DEFECT DYNAMICS IN 2-DIMENSIONAL CONVECTIVE ROLL PATTERNS

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