Monopoles, Strings and Gravitational Waves in Non-minimal Inflation

TL;DR

This paper explores how certain grand unification models predict the survival of monopoles and cosmic strings through inflation, with observable gravitational wave signatures that can shed light on early universe symmetry breaking.

Contribution

It presents a model within $SO(10)$ GUT that predicts stable monopoles and cosmic strings surviving inflation, linking these to gravitational wave signals and current cosmological observations.

Findings

Scalar spectral index $n_s$ matches observations

Tensor-to-scalar ratio $r ightarrow 0.003$

Predicts detectable gravitational waves from cosmic strings

Abstract

We discuss how in $SO(10)$ grand unification an observable number density of topologically stable intermediate mass ( $\sim 10^{14}$ GeV) monopoles survive inflation driven by a Coleman-Weinberg potential and non-minimal coupling of the inflaton field to gravity. The scalar spectral index $n_s$ is in excellent agreement with the current observations, and the tensor to scalar ratio $r\gtrsim 0.003$. The model also predicts the presence of intermediate scale topologically stable cosmic strings, and their gravitational wave spectrum reflects the amount of cosmic inflation experienced by the associated symmetry breaking. The discovery of these primordial monopoles and the stochastic gravitational wave background from the strings would provide important new insights regarding the symmetry breaking patterns in the early universe.