{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b31d47720abfb3e3792eacbbe654e1765ed5d18bde72b580fb44238b509bdb04","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["b3791f1778bc4fdaf9902ddb85fd7e51008cc9db779ece0bce99c99898bdbed3","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"f09562ff474b11a0b7d806f3a20065d8aacb7a50bcc49bc92b78350ea82f13a3","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":["ai:gpt-5.5"],"external_id":"hep.strong-cp.pq-quality","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"The axion solution needs a symmetry to be almost exact, but gravity is expected to break all such global symmetries slightly. Even a tiny breaking would spoil the solution.","posed_since":"1992","precise":"Planck-suppressed operators $O \\sim \\Phi^n / M_{\\mathrm{Pl}}^{(n-4)}$ shift $\\theta_{\\mathrm{bar}}$ by $\\sim f_a^n / (M_{\\mathrm{Pl}}^{(n-4)} m_a^2 f_a^2)$; keeping $\\mid\\theta_{\\mathrm{bar}}\\mid < 10^{-10}$ for $f_a \\sim 10^{10}\\,\\mathrm{GeV}$ requires $n > \\sim 10$. An answer is a UV mechanism (gauge discrete symmetries, composite or extra-dimensional axions) that provably forbids operators up to the required n with predicted low-energy signatures.","problem_ref":"b3791f1778bc4fdaf9902ddb85fd7e51008cc9db779ece0bce99c99898bdbed3","references":"","settled_by":"A UV-complete model with the required protection and a distinct prediction, for example heavy axions or modified axion couplings, confirmed by experiment.","status_note":"","title":"How is the Peccei-Quinn symmetry protected from gravitational breaking?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"4b95f18c9bcdb473f2f79234409da4005feee534e1d8e9759155715423728541","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"336f59e3719617f1b2e306305bc4f3968b24da18647dd28a670d5464e843cb42","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"-W7V_0PjDiKziXnbX2qR9UK62K_UkQ36cdzqbFkiMal_-3d-78R6UJWGMITMvfG8oZBSpIdm-dXoC_SVNbMUBg"},"schema":"pubphys.envelope/1"},"record_hash":"4b95f18c9bcdb473f2f79234409da4005feee534e1d8e9759155715423728541","leaf_index":3384}