Researchers Propose New Solution to Monopole Problem in Grand Unified Theories Using SU(5) GUT Framework
Researchers have proposed a solution to the long-standing cosmological monopole problem using an SU(5) Grand Unified Theory framework with symmetry breaking into a special subgroup. The monopole problem arises because GUTs predict far more magnetic monopoles than are observed, and standard inflationary solutions fail when inflation precedes GUT symmetry breaking. The proposed mechanism could also produce detectable gravitational-wave signals in future experiments, offering a potential observational test.
A new preprint posted to arXiv presents a solution to the magnetic monopole overproduction problem predicted by Grand Unified Theories (GUTs), which has been a persistent challenge in theoretical cosmology. The authors employ the Langacker–Pi mechanism within an SU(5) GUT framework, where the gauge symmetry first breaks to the Standard Model group and then further breaks to an intermediate subgroup SO(3)_C × SO(2)_L. During this intermediate phase, monopoles become connected to antimonopoles via cosmic strings, dramatically enhancing their mutual annihilation and reducing their abundance to acceptable levels. The symmetry is subsequently restored to the Standard Model gauge group, with the restoration transition being either first-order or second-order depending on model parameters. Crucially, a first-order phase transition would generate a stochastic gravitational-wave background, and for certain regions of parameter space this signal falls within the projected sensitivity of future gravitational-wave detectors. The model is realized by introducing a symmetric tensor scalar, a singlet scalar, and multiple singlet fermions into the SU(5) framework. The work spans 32 pages with 5 figures and carries institutional report numbers YITP-26-53 and OU-HET-1307.
What's missing
As a preprint, the work has not yet undergone peer review. Open questions include whether the intermediate symmetry-breaking phase introduces new phenomenological conflicts with collider data or proton decay constraints, and whether the multiple singlet fermions introduced have implications for dark matter or neutrino mass generation.
What different sources said
- arXiv astro-phCenter
A simple solution to the monopole problem: SU(5) GUT with symmetry breaking into special subgroup
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