SU(5)⊗Z13grand unification model

Abstract

We propose an SU 5 grand unified model with an invisible axion and the unification of the three coupling constants which is in agreement with the values, at M Z , of , s , and sin 2 W . A discrete, anomalous, Z 13 symmetry implies that the Peccei-Quinn symmetry is an automatic symmetry of the classical Lagrangian protecting, at the same time, the invisible axion against possible semiclassical gravity effects. Although the unification scale is of the order of the Peccei-Quinn scale the proton is stabilized by the fact that in this model the standard model fields form the SU 5 multiplets completed by new exotic fields and, also, because it is protected by the Z 13 symmetry.

Flavourful axion phenomenology

“…Considering the observed accuracy of strong-CP invariance, it is enough to protect the PQ symmetry up to some higherdimensional operators [12][13][14]. In this regard, it is appealing to consider an approximate PQ symmetry guaranteed by discrete (gauge) symmetries [15][16][17][18][19][20][21]. Alternatively, attempts to link PQ symmetry protected by continuous gauge symmetries to the flavour problem were made in [22,23].…”

Electronic phase separation transition as the origin of the superconductivity and pseudogap phase of cuprates

“…The experimental signals that can be linked with a phase separation are observed at the upper pseudogap T 0 (p) (in the notation of Ref.[1]) and consequently the ionic segregation transition must occur at a higher temperature T P S (p). Since T 0 (p) ( and T P S (p)) falls to zero in the overdoped regime and ionic mobility requires high temperatures, we assumed previously a charge disorder for underdoped compounds and an uniform charge distribution for p ≥ 0.20 [5,6,7]. However, new scanning tunneling microscopy (STM) data have shown an inhomogeneous local gap structure that remains in the far overdoped regime [8,9,10] which cannot be explained by an ionic phase separation, due to the low values of T 0 (p) for large p.These STM results on different doping regimes have clearly observed local gaps with different amplitudes at temperatures below and above T c (p)[9, 10] that ruled out ionic phase separation as the sole origin of the cuprate inhomogeneities.…”

The quest for an intermediate-scale accidental axion and further ALPs

“…This value is surprisingly close to the PQ scales and indicates that the model can be embedded in a grand unification group, so pointing to a connection between such scales [149]. In this connection it is important to note that dangerous operators leading to baryon number violation processes [150] are forbidden by the discrete symmetry Z 13 ⊗ Z 5 ⊗ Z ′ 5 to very high mass dimensions.…”