Implications of Gravitational Waves for Supersymmetric Grand Unification

TL;DR

This paper explores how recent gravitational wave observations can inform and constrain supersymmetric $SO(10)$ grand unification models, especially regarding symmetry breaking scales, cosmic strings, and monopole abundance.

Contribution

It demonstrates that gravitational wave data can restrict the symmetry breaking scale and parameters of supersymmetric $SO(10)$ unification models, linking cosmological signals to particle physics.

Findings

High intermediate scale above 10^{14} GeV is favored by gravitational wave data.

Spectrum observations can narrow cosmic string scale and unify couplings.

Monopole abundance constraints complement proton decay limits.

Abstract

Supersymmetric grand unification based on $SO(10)$ is one of the most attractive paradigms in physics beyond the Standard Model. Inspired by the recent NANOGrav signal, we discuss the implications of detecting a stochastic gravitational wave background emitted by a network of cosmic strings for the $SO(10)$ grand unification. Starting from a minimal model with multiple steps of symmetry breaking, we show that it generally prefers a high intermediate scale above $10^{14}\, \mathrm{GeV}$ that is favored by observable primordial gravitational waves. The observed spectrum can potentially narrow the possible range of the cosmic string scale and restricts the unified couplings and the unification scale by requiring gauge coupling unification. As an indirect consequence of the high cosmic string scale, the monopole abundance places non-trivial constraints on the theory. These are complementary to the proton decay constraints and probe different facets of supersymmetric $SO(10)$ unification theories.