Gradient free energy of nematic liquid crystals with topological defects

Abstract

The authors investigate the gradient free energy of uniaxial nematics in the presence of topological defects and they find a new cross-coupling term not reported before; gradients of the order parameter couple to gradients of the director field n thus connecting two different characteristic length scales. The implications of the novel terms for the existence of a gauge-covariant formulation of condensed matter systems with topological defects as well as their occurrence for various systems are discussed.