Elastic anisotropy at a glance : the optical signature of disclination lines

Nematic liquid crystals often host topological defects in the form of disclination lines. Because of the elastic anisotropy intrinsic to nematics, the tight distortions of the molecular ordering around the defect lines couple to the mean nematic orientation inducing deformations on length scales easily observed in conventional optical microscopy. By a synergy of experiments, numerical computations and theoretical modeling we present a quantitative analysis of this phenomenon, clarifying the key role played by twist deformations. We provide simple analytical tools to predict the amplitude of this deformations and the energy involved in it. The effects here described are potentially essential ingredients to all liquid crystal applications involving topological defects.