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  • Open Access

Noninflationary solution to the monopole problem

Daniele Perri*

  • Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ulica Pasteura 5, PL-02-093 Warsaw, Poland

  • *Contact author: daniele.perri@fuw.edu.pl
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Phys. Rev. D 113, 023547 – Published 30 January, 2026

DOI: https://doi.org/10.1103/zcp4-pkbw

Abstract

Magnetic monopoles are a long-standing prediction of Grand Unified Theories, yet their efficient production in early universe phase transitions would lead to a monopole abundance that far exceeds observational limits. The standard solution of the problem invokes inflation occurring after monopole production, diluting their density to undetectable levels and eliminating any possibility of present-day observation. Here, we propose an alternative solution based on the breaking, in the early universe prior to big bang nucleosynthesis, of the Weyl conformal symmetry of the gauge kinetic sector of the Lagrangian. This mechanism enhances monopole annihilation, thereby reducing their abundance to acceptable levels without requiring inflation. This scenario also predicts a residual flux of Grand Unified Theories monopoles potentially within the sensitivity of current and upcoming cosmic ray detectors, making their discovery possible in the near future.

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Phys. Rev. D 113, 023547– Published 30 January, 2026
  • Received 20 October 2025
  • Accepted 5 December 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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