On Stability of Fermionic Superconducting Current in Cosmic String

TL;DR

This paper investigates the stability of superconducting currents in cosmic strings within axion models, revealing conditions under which the currents and associated vortons remain stable or decay, impacting cosmological implications.

Contribution

It provides a detailed analysis of the stability conditions of superconducting currents in cosmic strings, especially considering particle decay in curved versus straight configurations.

Findings

Superconductivity is stable in straight or small-core strings despite particle instability.

Curved strings cause carrier particle decay, reducing vorton lifetime.

Vorton stability closely relates to the vacuum decay properties of carrier particles.

Abstract

Recently, the chiral superconductivity of the cosmic string in the axion model has gathered attention. The superconductive nature can alter the standard understanding of the cosmology of the axion model. For example, a string loop with a sizable superconducting current can become a stable configuration, which is called a Vorton. The superconductive nature can also affect the cosmological evolution of the string network. In this paper, we study the stability of the superconducting current in the string. We find the superconductivity is indeed stable for a straight string or infinitely small string core size, even if the carrier particles are unstable in the vacuum. However we also find that the carrier particle decays in a curved string in typical axion models, if the carrier particles are unstable in the vacuum. Accordingly, the lifetime of the Vorton is not far from that of the carrier particle in the vacuum.