Researchers Propose New Solution to Monopole Problem in Grand Unified Theories Using SU(5) GUT Framework
Physicists have proposed a mechanism within SU(5) Grand Unified Theory that addresses the monopole problem—the prediction of excessive magnetic monopoles in the early universe—by using intermediate symmetry breaking that allows monopoles and antimonopoles to annihilate via cosmic strings. The solution builds on the Langacker-Pi mechanism and involves breaking gauge symmetry through multiple stages with specific scalar and fermion fields. The approach is significant because it offers an alternative to inflation-based solutions and could produce detectable gravitational wave signals testable by future experiments.
A new theoretical proposal addresses a longstanding problem in Grand Unified Theories (GUTs): the overproduction of magnetic monopoles in the early universe. The researchers propose using an SU(5) GUT framework with a carefully designed symmetry-breaking sequence. After initial breaking to the Standard Model gauge group, the symmetry is further broken to SO(3)_C×SO(2)_L through an intermediate phase. During this intermediate phase, monopoles become connected to antimonopoles by cosmic strings, dramatically enhancing their pair annihilation and reducing their abundance. The model incorporates an adjoint scalar, a symmetric tensor scalar, a singlet scalar, and multiple singlet fermions. Depending on model parameters, the final symmetry restoration can occur via either first-order or second-order phase transitions, with first-order transitions generating stochastic gravitational wave signals potentially detectable by future gravitational wave observatories.
What's missing
The study does not discuss how this mechanism compares quantitatively to existing inflation-based solutions in terms of monopole abundance reduction, nor does it address potential constraints from other cosmological observations or particle physics experiments that might test this framework.
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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