Grand unification theory

Grand Unification, grand unified theory, or GUT is one of several very similar unified field theories or models in physics that unify what are considered three "fundamental" gauge symmetries: hypercharge, the weak force, and quantum chromodynamics (QCD). Grand unification is based on the idea that at extremely high energies, all symmetries have the same gauge coupling strength, which is consistent with the speculation that they are really different manifestations of a single overarching gauge symmetry. More specifically, GUTs predict that at energies above GeV, the electromagnetic, weak nuclear, and strong nuclear forces are fused into a single unified field. (Parker, B 1993, 'Overcoming some of the problems', pp.259-279)
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