Can type II Semi-local cosmic strings form?

TL;DR

This paper investigates the formation of type II semi-local cosmic strings, demonstrating that their inherent instabilities prevent their existence in a cosmological setting, thus impacting models involving such defects.

Contribution

The study introduces a minimal model for semi-local strings with current-carrying properties and shows that these strings are inherently unstable, preventing their formation in the universe.

Findings

Condensate formation leads to a chiral configuration.

Current induces a longitudinal instability.

Type II semi-local strings cannot form cosmologically.

Abstract

We present the simplest possible model for a semi-local string defect in which a U(1) gauged subgroup of an otherwise global SU(2) is broken to produce local cosmic strings endowed with current-carrying properties. Restricting attention to type II vortices for which the non current-carrying state is unstable, we show that a condensate must form microscopically and macroscopically evolve towards a chiral configuration. It has been suggested that such configurations could potentially exist in a stable state, thereby inducing large cosmological consequences based on equilibrium angular momentum supported loop configurations (vortons). Here we show that the current itself induces a macroscopic (longitudinal) instability: we conclude that type II semi-local cosmic strings cannot form in a cosmological context.