New solutions for non-Abelian cosmic strings

TL;DR

This paper explores new classical solutions for non-Abelian cosmic strings, revealing complex monopole and string interactions, symmetry breakings, and the emergence of semipoles and supercurrents in gauge theories relevant to grand unified theories.

Contribution

It introduces novel string and monopole solutions, including semipoles and supercurrents, in non-Abelian gauge theories with potential applications to GUT models.

Findings

Identification of degenerate string solutions and monopoles

Discovery of semipoles as kink solutions with complex flux and Z4 charge

Supercurrents arising at special Higgs coupling values

Abstract

We study the properties of classical vortex solutions in a non-Abelian gauge theory. A system of two adjoint Higgs fields breaks the SU(2) gauge symmetry to $Z_2$, producing 't Hooft-Polyakov monopoles trapped on cosmic strings, termed beads; there are two charges of monopole and two degenerate string solutions. The strings break an accidental discrete $Z_2$ symmetry of the theory, explaining the degeneracy of the ground state. Further symmetries of the model, not previously appreciated, emerge when the masses of the two adjoint Higgs fields are degenerate. The breaking of the enlarged discrete symmetry gives rise to additional string solutions and splits the monopoles into four types of `semipole': kink solutions that interpolate between the string solutions, classified by a complex gauge invariant magnetic flux and a $Z_4$ charge. At special values of the Higgs self-couplings, the accidental symmetry broken by the string is continuous, giving rise to supercurrents on the strings. The SU(2) theory can be embedded in a wide class of Grand Unified Theories, including SO(10). We argue that semipoles and supercurrents are generic on GUT strings.