Observing Correlated Production of Defects-Antidefects in Liquid Crystals

We present observations of strength one defects and antidefects formed in isotropic-nematic phase transition in a thin layer of nematic liquid crystals, using a cross-polarizer setup. We measure the widths of the distributions of {\it net} winding number in small regions, and determine the exponent characterizing the correlation between defects and antidefects to be 0.26$\pm$0.11, in very good agreement with the value 1/4 predicted by the Kibble mechanism for defect production. We also describe a novel technique to determine the director distribution in observations of defect networks.