Primordial monopoles, black holes and gravitational waves

TL;DR

This paper explores how hybrid inflation models based on grand unified theories can produce observable primordial monopoles, black holes, and gravitational waves, potentially explaining dark matter and baryon asymmetry.

Contribution

It demonstrates a mechanism for generating topologically stable monopoles and black holes during hybrid inflation, linking grand unification to observable cosmological phenomena.

Findings

Monopoles with mass ~4×10^{17} GeV and magnetic charge are produced.

Primordial black holes with mass 10^{17}-10^{19} g can account for dark matter.

Gravitational wave spectrum from waterfall transition is predicted.

Abstract

We show how topologically stable superheavy magnetic monopoles and primordial black holes can be generated at observable levels by the waterfall field in hybrid inflation models based on grand unified theories. In $SU(5) \times U(1)_\chi$ grand unification, the monopole mass is of order $4 \times 10^{17}$ GeV, and it carries a single unit ($2 \pi /e$) of Dirac magnetic charge as well as screened color magnetic charge. The monopole density is partially diluted to an observable value, and accompanied with the production of primordial black holes with mass of order $10^{17}$-$10^{19}$ g which may make up the entire dark matter in the universe. The tensor to scalar ratio $r$ is predicted to be of order $10^{-5}$ - $10^{-4}$ which should be testable in the next generation of CMB experiments such as CMB-S4 and LiteBIRD. The gravitational wave spectrum generated during the waterfall transition is also presented. The observed baryon asymmetry can be explained via leptogenesis.