Axion dark matter, proton decay and unification

Abstract

We discuss the possibility to predict the QCD axion mass in the context of grand unified theories. We investigate the implementation of the DFSZ mechanism in the context of renormalizable SU(5) theories. In the simplest theory, the axion mass can be predicted with good precision in the range m a = (2-16) neV, and there is a strong correlation between the predictions for the axion mass and proton decay rates. In this context, we predict an upper bound for the proton decay channels with antineutrinos, τ (p → K +ν) 4 × 10 37 yr and τ (p → π +ν) 2 × 10 36 yr. This theory can be considered as the minimal realistic grand unified theory with the DFSZ mechanism and it can be fully tested by proton decay and axion experiments.

Axion model with the ${\rm SU}(6)$ unification

“…If one allows further fine-tuning of |k sin(δ)| ∼ O(10 −4 ), the axion masses may be even as light as m a ∼ O(10 −5 ) eV (dashed line), and reach the sensitive regions of the Plasma halo scope [100]. The SU(6) axion mass is distinguishable from the previous predictions from the SU(5) GUT [15,17,19,20] with m a ∼ O(10 −9 ) eV.…”

“…The grand unification theories (GUT) were considered as framework for the axion models based on the SU(5) [9] and SO (10) [10] unifications. Later, other varieties based on the SU (5) [11][12][13][14][15][16][17][18][19][20], SO (10) [18,[21][22][23][24][25][26], and E 6 [27] were also studied. In most of the previous SU (5) and SO (10) GUT model buildings, the global U(1) PQ symmetry commutes with the GUT group.…”

Accidental SO(10) axion from gauged flavour

“…One could try to follow a similar path for GUTs. SU(5) is broken to the SM in one step, either via a 24 or a 75, both of which have however a trivial center (in fact, all SU (5) representations containing a SM-singlet direction have also zero quintality), thus making structurally difficult to get an automatic U(1) PQ in SU (5) where the PQ symmetry is broken via a complex adjoint [69][70][71][72]. Non-minimal GUTs such as SU (6) or E 6 are more promising in this respect, since they feature representations with SM-singlet directions (which can achieve large VEVs compared to the electroweak scale) and at the same time transform non-trivially under their respective Z 6 and Z 3 centers.…”

Pati-Salam axion

“…Subsequently, refs. [52,53] considered axion mass predictions in other minimal renormalizable SU(5)×U(1) PQ models. Some cosmological consequences of supersymmetric axion GUTs were considered instead in [54].…”