Automatic Peccei–Quinn symmetry
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 ; This project has received support from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant agreements no. 690575 (RISE InvisiblesPlus) and no. 674896 (ITN ELUSIVES). M.B.G and P. Q. also acknowledge support from the the Spanish Research Agency (Agencia Estatal de Investigación) through the grant IFT Centro de Excelencia Severo Ochoa SEV-2016-0597, as well as from the "Spanish Agencia Estatal de Investigación" (AEI) and the EU "Fondo Europeo de Desarrollo Regional" (FEDER) through the project FPA2016-78645-P. The work of P.Q. was supported through a "La Caixa-Severo Ochoa" predoctoral grant of Fundación La Caixa. This research was also supported in part by WPI Research Center Initiative, MEXT, Japan (MI, MY and TTY), and in part by JSPS Grant-in-Aid for Scientific Research no. 15h05889, no. 16h03991, no. 18H05542 (MI), no. 26104001, no. 26104009, no. 16H02176 (TTY), and no. 17H02878 (MI and TTY). TTY is a Hamamatsu Professor at Kavli IPMU