Fine structure of local and axion strings.

Abstract

We examine the nature of the internal structure of strings arising from field theories when a global or local symmetry is spontaneously broken. The classical dynamics of these strings is represented by effective Lagrangians in which the standard Nambu-Goto term is supplemented by additional terms that are geometric in nature. In the simplest case of the local string, the new term is just the extrinsic curvature of the world sheet. For the axion string, terms of the same order as the extrinsic curvature must be added involving the coupling of the axion to the curvature itself.