Automatic Peccei-Quinn symmetry

Understand

We present a dynamical (composite) axion model where the Peccei-Quinn (PQ) symmetry arises automatically as a consequence of chirality and gauge symmetry.

• The Standard Model is simply extended by a confining and chiral $SU(5)$ gauge symmetry.
• The PQ symmetry coincides with a $B-L$ symmetry of the exotic sector.
• The theory is protected by construction from quantum gravitational corrections stemming from operators with mass dimension lower than nine.