Experimental studies of defect dynamics and interaction in electrohydrodynamic convection

A report about experimental studies of the dynamics and interaction of topological defects in the roll structure of electrohydrodynamic convection in nematic liquid crystals is given. It is found that the motion of defects of opposite topological charges towards annihilation has two stages. At large distances they move with a constant velocity that depends mainly linearly on the wave-number mismatch. At a later stage, when the defects come closer, they are accelerated due to attraction. In order to compare these results quantitatively with available theories that are based on the Ginzburg-Landau equation, all coefficients of this equation are measured.