Variations on the SU(5) axion

International audienceThe simultaneous embeddings of an axion state and a seesaw mechanism within the SU(5) Grand Unification Theory, both minimal and flipped, are systematically studied. Generically, seesaw mechanisms prevents a manifest axion Peccei–Quinn (PQ) symmetry at the GUT scale, but this does not mean no axion could emerge at the low scale. Several viable DFSZ-like scenarios are identified, both in the minimal and flipped case, and with various seesaw mechanisms, by carefully analyzing the global and local U(1) symmetries at play and their fate after the various stages of symmetry breaking. Interestingly, though these scenarios are quite different phenomenologically, and each assign specific non-manifestly SU(5) symmetric PQ charges to the SM fermions, the resulting low energy axion phenomenology is found to be particularly resilient and universal