Further Issues: Defect Phase/Orientation, Charge Density, Curvature

This chapter discusses three advanced topics in the theory of defects in the xy model. First, it considers the concept of defect phase or orientation, and shows how relative phase affects the interaction between defects. Second, it demonstrates the concept of topological charge density for defects in the xy model, analogous to electric charge density. Third, it explores how defects interact with a curved surface, and distinguishes among three different types of interactions.