We find that the self-intersection of a closed curve (loop) is characterized by a jump in the self-linkage number of the loop. This is used to study the self-intersections of a mathematical closed curve evolving according to the Nambu action. We also show that segments of cosmic string cannot simply pass through one another at a self-intersection. Instead, intercommuting is found to be energetically favorable in the case of untwisted global strings.

• Received 28 November 1988

DOI:https://doi.org/10.1103/PhysRevD.39.1768