Flipped SU(5)

The Flipped SU(5) model is a grand unified theory (GUT) first contemplated by Stephen Barr in 1982,[1] and by Dimitri Nanopoulos and others in 1984.[2][3] Ignatios Antoniadis, John Ellis, John Hagelin, and Dimitri Nanopoulos developed the supersymmetric flipped SU(5), derived from the deeper-level superstring.[4][5]

Some current efforts to explain the theoretical underpinnings for observed neutrino masses are being developed in the context of supersymmetric flipped SU(5).[6]

Flipped SU(5) is not a fully unified model, because the U(1)Y factor of the Standard Model gauge group is within the U(1) factor of the GUT group. The addition of states below Mx in this model, while solving certain threshold correction issues in string theory, makes the model merely descriptive, rather than predictive.[7]

This assignment includes three right-handed neutrinos, which have never been observed, but are often postulated to explain the lightness of the observed neutrinos and neutrino oscillations. There is also a 101 and/or 10−1 called the Higgs fields which acquire a VEV, yielding the spontaneous symmetry breaking

The SU(5) representations transform under this subgroup as the reducible representation as follows:

The name "flipped" SU(5) arose in comparison to the "standard" SU(5) Georgi–Glashow model, in which uc and dc quark are respectively assigned to the 10 and 5 representation. In comparison with the standard SU(5), the flipped SU(5) can accomplish the spontaneous symmetry breaking using Higgs fields of dimension 10, while the standard SU(5) requires both a 5- and 45-dimensional Higgs.

There are also the additional fields 5−2 and 52 containing the electroweak Higgs doublets.

Calling the representations for example, 5−3 and 240 is purely a physicist's convention, not a mathematician's convention, where representations are either labelled by Young tableaux or Dynkin diagrams with numbers on their vertices, and is a standard used by GUT theorists.

this model does not predict monopoles. See 't Hooft–Polyakov monopole.

Z2 (matter parity) not related to U(1)R in any way for this particular model

A generic invariant renormalizable superpotential is a (complex) SU(5) × U(1)χ × Z2 invariant cubic polynomial in the superfields which has an R-charge of 2. It is a linear combination of the following terms:

The second column expands each term in index notation (neglecting the proper normalization coefficient). i and j are the generation indices. The coupling Hd 10i 10j has coefficients which are symmetric in i and j.

In those models without the optional φ sterile neutrinos, we add the nonrenormalizable couplings instead.