Magnetic monopoles and high frequency gravitational waves from quasi-stable strings

TL;DR

This paper investigates the formation and cosmological implications of quasi-stable cosmic strings and monopoles from GUT symmetry breaking, predicting observable gravitational waves in the Hz to kHz range.

Contribution

It introduces a novel scenario of monopole-string networks from $SO(10)$ GUT breaking, analyzing their potential to produce detectable gravitational waves.

Findings

Monopoles with single and double Dirac charge emerge from specific symmetry breaking patterns.

A parameter space exists where these monopoles and strings could produce observable gravitational waves.

The gravitational wave signals are in the Hz to kHz range, accessible to current and future detectors.

Abstract

The spontaneous breaking of $SO(10)$ via flipped $SU(5)$ to the Standard Model yields a novel scenario in which the superheavy topologically stable GUT monopole carrying a single unit ($2\pi/e$) of Dirac magnetic charge emerges from the merger of a confined but topologically distinct monopole-antimonopole pair that are pulled together by a string. The $SO(10)$ breaking via the subgroup $SU(4)_c\times SU(2)_L\times SU(2)_R$, following a similar reasoning, produces a topologically stable monopole that carries two units ($4\pi/e$) of Dirac charge. We explore the cosmological consequences of this scenario by assuming that the monopoles and strings experience a limited number of inflationary $e$-foldings, before re-entering the horizon and ultimately forming a network of quasi-stable strings bounded by monopole-antimonopole pairs. We identify regions of the parameter space that yield an observable number density of the GUT monopole from the collapse of the appropriate string segments. The gravitational waves emitted by these quasi-stable cosmic strings lie in the Hz to kHz range, which can be tested in a number of proposed and ongoing experiments.