Dynamics of line defects in nematic liquid crystals

Abstract

An experiment is performed in which a topological line defect (S=-(1/2)) is forced to move with constant speed c under the action of an applied voltage V. We argue that the line speed is determined by a competition between the viscous damping and the free energy that the system gains by displacing the line, so that c=\ensuremath{\beta}V, with \ensuremath{\beta}=1/2\ensuremath{\gamma}b(${\mathrm{\ensuremath{\epsilon}}}_{\mathrm{a}}$K/\ensuremath{\pi}${)}^{1/2}$ and b a number \ensuremath{\sim}1 determined only by viscous effects close to the core of the defect.