Superconducting strings in E6

Abstract

We discuss the appearance of superconducting strings in E6 grand unification, keeping track of the magnetic monopole flux that precedes the formation of the string flux tube. This flux matching ensures compatibility with the quantum tunneling of a monopole-antimonopole pair on a metastable string. We identify two realistic E6 models with superconducting (metastable) strings that also carry zero modes of the right-handed Majorana neutrinos and dark matter particles. Depending on the symmetry breaking scale associated with the strings, the latter could be a source of observable gravitational waves, intermediate scale dark matter, and the observed baryon asymmetry via leptogenesis. Topologically stable superconducting strings also appear if the E6 symmetry breaking leaves unbroken the Z2 subgroup of Z4, the center of SO(10). The zero modes of the Standard Model fermions are the charge carriers in this case. Finally, the flux matching condition ensures that the Aharonov-Bohm phase change in going around the metastable strings is an integer multiple of 2π for all fields. The fields in the spinorial representation of SO(10) acquire a phase change of exp(±iπ) if taken around the topologically stable Z2 string.

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