Predictive Non-Minimal SU(5) GUT
Abstract
Breaking of SU(5) down to the Standard Model gauge group can be implemented by any non-trivial self-conjugate scalar representation with a suitable vacuum expectation value. The Georgi-Glashow model accomplishes this breaking with a 24-dimensional representation. That choice, although the most economical one, fails to unify the gauge coupling constants. Moreover, subsequent breaking of the Standard Model down to SU(3) × U(1)em with a $5$-dimensional representation fails to simultaneously provide viable masses for the down-type quarks and the charged leptons. We show that the substitution of the $24$-dimensional representation with a $75$-dimensional representation fixes the gauge coupling unification issue outrightly. We furthermore pin down, by computing the full mass spectrum of the multiplets in $75$-dimensional representation, the range of the unification scale mGUT to be 1015 GeV ≲ mGUT ≲ 1016 GeV. This unification window is partially excluded by Super-Kamiokande data and will be experimentally accessible at Hyper-Kamiokande. The second issue with the Georgi-Glashow model can be addressed, for example, with vectorlike fermions. The $24$-dimensional scenario admits three different types of vectorlike fermions that can properly account for the mismatch between the down-type quark and the charged lepton masses. The $75$-dimensional scenario, on the other hand, offers enhanced predictivity by allowing only a unique vectorlike addition of 10F + 10̅F that restores realistic charged fermion masses and modestly pushes the upper limit on the unification scale to mGUT ≲ 3×1016 GeV. The proposed framework with $75$-dimensional scalar representation can thus serve as a phenomenologically viable alternative to the standard Georgi-Glashow symmetry breaking paradigm.
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BibTeX
@misc{dorsner2026predictive,
title = {{Predictive Non-Minimal SU(5) GUT}},
author = {Ilja Doršner and Mijo Matković and Shaikh Saad},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.13376},
eprint = {2609.13376},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.13376},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Predictive Non-Minimal SU(5) GUT
AU - Ilja Doršner
AU - Mijo Matković
AU - Shaikh Saad
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2609.13376
UR - https://arxiv.org/abs/2609.13376
AB - Breaking of SU(5) down to the Standard Model gauge group can be implemented by any non-trivial self-conjugate scalar representation with a suitable vacuum expectation value. The Georgi-Glashow model accomplishes this breaking with a 24-dimensional representation. That choice, although the most economical one, fails to unify the gauge coupling constants. Moreover, subsequent breaking of the Standard Model down to SU(3) × U(1)_em with a $5$-dimensional representation fails to simultaneously provide viable masses for the down-type quarks and the charged leptons. We show that the substitution of the $24$-dimensional representation with a $75$-dimensional representation fixes the gauge coupling unification issue outrightly. We furthermore pin down, by computing the full mass spectrum of the multiplets in $75$-dimensional representation, the range of the unification scale m_GUT to be 10^15 GeV ≲ m_GUT ≲ 10^16 GeV. This unification window is partially excluded by Super-Kamiokande data and will be experimentally accessible at Hyper-Kamiokande. The second issue with the Georgi-Glashow model can be addressed, for example, with vectorlike fermions. The $24$-dimensional scenario admits three different types of vectorlike fermions that can properly account for the mismatch between the down-type quark and the charged lepton masses. The $75$-dimensional scenario, on the other hand, offers enhanced predictivity by allowing only a unique vectorlike addition of 10_F + 10̅_F that restores realistic charged fermion masses and modestly pushes the upper limit on the unification scale to m_GUT ≲ 3×10^16 GeV. The proposed framework with $75$-dimensional scalar representation can thus serve as a phenomenologically viable alternative to the standard Georgi-Glashow symmetry breaking paradigm.
ER -