Probing Stochastic Gravitational Wave Background from $SU(5) \times U(1)_{\chi}$ Strings in Light of NANOGrav 15-Year Data

TL;DR

This paper models a specific grand unified theory with cosmic strings that decay and produce a gravitational wave background, matching recent pulsar timing array observations and accessible to future experiments.

Contribution

It introduces a realistic $SU(5) imes U(1)_{ ext{chi}}$ model with metastable cosmic strings that generate observable gravitational waves consistent with NANOGrav data.

Findings

Cosmic string network decay produces a gravitational wave background compatible with NANOGrav.

The model predicts a gravitational wave spectrum detectable by current and future experiments.

Incorporating non-minimal Higgs inflation solves the monopole problem and aligns the string tension with observations.

Abstract

A realistic model of $SU(5) \times U(1)_{\chi}$, embedded in $SO(10)$ supersymmetric grand unified theory, is investigated for the emergence of a metastable cosmic string network. This network eventually decays via the Schwinger production of monopole-antimonopole pairs, subsequently generating a stochastic gravitational wave background that is compatible with the NANOGrav 15-year data. In order to avoid the monopole problem in the breaking of both $SO(10)$ and $SU(5)$, a non-minimal Higgs inflation scenario is incorporated. The radiative breaking of the $U(1)_{\chi}$ symmetry at a slightly lower scale plays a pivotal role in aligning the string tension parameter with the observable range. The resultant gravitational wave spectrum not only accounts for the signal observed in the most recent pulsar timing array (PTA) experiments but is also accessible to both current and future ground-based and space-based experiments.