Primordial Monopoles and Strings, Inflation, and Gravity Waves

TL;DR

This paper explores how magnetic monopoles and cosmic strings from grand unified theories can survive inflation and produce observable gravitational waves, linking particle physics with cosmological signals.

Contribution

It analyzes the survival of monopoles and strings in specific GUT models and estimates their gravitational wave signatures considering inflation driven by a Coleman-Weinberg potential.

Findings

Monopoles with mass ~10^{13}-10^{14} GeV can survive inflation.

Cosmic strings with Gμ ~ 10^{-11}-10^{-10} are present at observable levels.

Predicted gravity wave spectrum depends on inflationary parameters, with r between 0.06 and 0.003.

Abstract

We consider magnetic monopoles and strings that appear in non-supersymmetric $SO(10)$ and $E_6$ grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter $G\mu$ spans the range $10^{-6}-10^{-30}$, where $G$ is Newton's constant and $\mu$ is the string tension. We show how intermediate scale monopoles with mass $\sim 10^{13}-10^{14}$ GeV and flux $\lesssim 2.8\times 10^{-16}$ ${\mathrm{cm}^{-2}\mathrm{s}^{-1}\mathrm{sr}^{-1}}$, and cosmic strings with $G\mu \sim 10^{-11}-10^{-10}$ survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio $r$ lies between $0.06$ and $0.003$ depending on the details of the inflationary scenario.