Gravitational waves from breaking of an extra $U(1)$ in $SO(10)$ grand unification

TL;DR

This paper explores how breaking an extra U(1) symmetry within an SO(10) grand unified theory can produce detectable gravitational waves, linking grand unification, neutrino masses, and observable cosmic signals.

Contribution

It presents a UV-complete SO(10) GUT model that predicts a strong first-order phase transition generating observable gravitational waves.

Findings

Gravitational wave signals are detectable with current or future experiments.

The GW amplitude decreases and peak frequency increases with higher right-handed neutrino masses.

The model successfully unifies the Standard Model with an extra U(1) symmetry in a consistent GUT framework.

Abstract

In a class of gauged $U(1)$ extended Standard Models (SMs), the breaking of the $U(1)$ symmetry is not only a source for Majorana masses of right-handed (RH) neutrinos crucial for the seesaw mechanism, but also a source of stochastic gravitational wave (GW) background. Such $U(1)$ extended models are well-motivated from the viewpoint of grand unification. In this paper, we discuss a successful ultraviolet completion of a $U(1)$ extended SM by an $SO(10)$ grand unified model through an intermediate step of $SU(5) \times U(1)$ unification. With a parameter set that is compatible with the $SO(10)$ grand unification, we find that a first-order phase transition associated with the $U(1)$ symmetry breaking can be strong enough to generate GWs with a detectable size of amplitude. We also find that the resultant GW amplitude reduces and its peak frequency becomes higher as the RH neutrino masses increase.