GUTs without guts
arXiv:1401.1782 · doi:10.1016/j.nuclphysb.2014.03.026
Abstract
The structure of a Standard Model family is derived in a class of brane models with a U(M) x U(N) factor, from two mildly anthropic requirements: a massless photon and a universe that does not turn into a plasma of massless charged particles. If we choose M=3 and N=2, the only option is shown to be the Standard Model with an undetermined number of families. We do not assume the U(1) embedding, charge quantization, family repetition, nor the fermion representations; all of these features are derived, assuming a doublet Higgs. With a slightly stronger assumption even the Higgs representation is determined. We also consider a more general class, requiring an asymptotically free strong SU(M) (with M geq 3) interaction from the first factor and an electromagnetic U(1) embedded in both factors. We allow Higgs symmetry breaking of the U(N)x U(1) flavor group by at most one Higgs boson in any representation, combined with any allowed chiral symmetry breaking by SU(M). For M=3 there is a large number of solutions with an unbroken U(1). In all of these, quarks have third-integral charges and color singlets have integer charges in comparison to leptons. Hence Standard Model charge quantization holds for any N. Only for N=2 these models allow an SU(5) GUT extension, but this extension offers no advantages whatsoever for understanding the Standard Model; it only causes complications, such as the doublet-triplet splitting problem. Although all these models have a massless photon, all except the Standard Model are ruled out by the second anthropic requirement. In this class of brane models the Standard Model is realized as a GUT with its intestines removed, to keep only the good parts: a GUT without guts.
60 pages; v2: Minor corrections, references added
References in corpus (18)
- Four-dimensional String Compactifications with D-Branes, Orientifolds and Fluxes
- Flux Compactification
- Spacetime Instanton Corrections in 4D String Vacua - The Seesaw Mechanism for D-Brane Models
- A Mini-Landscape of Exact MSSM Spectra in Heterotic Orbifolds
- Neutrino Majorana Masses from String Theory Instanton Effects
- Stringy Instantons and Quiver Gauge Theories
- Orientifolds, hypercharge embeddings and the Standard Model
- Instanton Induced Neutrino Majorana Masses in CFT Orientifolds with MSSM-like spectra
- Non-perturbative Yukawa Couplings from String Instantons
- Stringy Instantons at Orbifold Singularities
- Why the Standard Model
- Statistical analysis of the supersymmetry breaking scale
- Classification of Heterotic Pati-Salam Models
- Stars In Other Universes: Stellar structure with different fundamental constants
- SU(5) D-brane realizations, Yukawa couplings and proton stability
- Anomaly Nucleation Constrains SU(2) Gauge Theories
- Why do we observe a weak force? The hierarchy problem in the multiverse
- Charge Quantization and the Standard Model from the and Nonlinear -Models