Gravitational capture of magnetic monopoles by primordial black holes in the early universe

• Published in: The journal of high energy physics Vol. 2023; no. 10; pp. 37 - 40
• Main Authors: Zhang, Chen, Zhang, Xin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 06.10.2023; Springer Nature B.V; SpringerOpen
• Subjects: Absorption cross sections; Black Holes; Broken symmetry; Classical and Quantum Gravitation; Cosmology of Theories BSM; Early Universe Particle Physics; Elementary Particles; High energy physics; Magnetic monopoles; Phase transitions; Phase Transitions in the Early Universe; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Regular Article - Theoretical Physics; Relativity Theory; String Theory; Universe; Cosmology of Theories BSM; Black Holes; Early Universe Particle Physics; Phase Transitions in the Early Universe
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP10(2023)037

A bstract It is intriguing to ask whether the existence of primordial black holes (PBHs) in the early universe could significantly reduce the abundance of certain stable massive particles (SMP) via gravitational capture, after which the PBHs evaporate before BBN to avoid conflict with stringent bounds. For example, this mechanism is relevant to an alternative solution of the monopole problem proposed by Stojkovic and Freese, in which magnetic monopoles produced in the early universe are captured by PBHs, thus freeing inflation from having to occur during or after the corresponding phase transitions that produced the monopoles. In this work, we reanalyze the solution by modelling the capture process in the same way as the coexisting monopole annihilation. A subtle issue which is not handled properly in the previous literature is the choice of an effective capture cross section for diffusive capture. We model this aspect properly and justify our treatment. A monochromatic PBH mass function and a radiation-dominated era before PBH evaporation are assumed. We find that for Pati-Salam monopoles corresponding to a symmetry breaking scale between 10 10 GeV and 10 15 GeV, the capture rate is many orders of magnitude below what is needed to cause a significant reduction of the monopole density. Within our assumptions, we also find that the magnetic charge that is large enough to make an extremal magnetic black hole cosmologically stable cannot be obtained from magnetic charge fluctuation via monopole capture. The large magnetic charged required by cosmological stability can nevertheless be obtained from magnetic charge fluctuation at PBH formation, and if later the monopole abundance can be reduced significantly by some non-inflationary mechanism, long-lived near-extremal magnetic black holes of observational relevance might result.