Gravitational wave emission from metastable current-carrying strings in $E_6$

TL;DR

This paper models gravitational wave emissions from metastable cosmic strings in an $E_6$ extension of the Standard Model, showing their spectrum can match current LIGO and PTA observations.

Contribution

It introduces an extended VOS model to estimate GW spectra from metastable strings with RHN currents in $E_6$ models, aligning predictions with recent observational data.

Findings

GW spectrum compatible with LIGO O3 data

Spectrum consistent with PTA signals at 1σ level

Metastable strings with specific tensions produce detectable GWs

Abstract

We discuss $E_6$ based extensions of the Standard Model (SM) containing two varieties of superheavy metastable cosmic strings (CSs) that respectively have neutral and electrically charged current carriers. We employ an extended version of the velocity-dependent one-scale (VOS) model, recently discussed by some authors, to estimate the gravitational wave (GW) spectrum emitted by metastable strings with a dimensionless string tension $G \mu \approx 10^{-6}$ that carry a right-handed neutrino (RHN) current. We find that with a low to moderate amount of current, the spectrum is compatible with the LIGO O3 run and also consistent at the 1$\sigma$ level with the recent PTA signals.