Electroweak axion string and superconductivity

TL;DR

This paper investigates electroweak axion strings in the DFSZ model, revealing their potential superconductivity without fermionic zero modes, and explores their stability, large currents, and possible network formations in the early universe.

Contribution

It introduces new electroweak axion string solutions, including a stable superconducting string with W-flux, and discusses their cosmological implications.

Findings

Electroweak axion strings can be superconducting without fermionic zero modes.

The W-flux string can be the lightest and stable in certain parameter regions.

Large electric currents along the strings can lead to attractive forces and Y-junction formations.

Abstract

We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zero modes. We construct three types of electroweak axion string solutions. Among them, the string with $W$-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.