{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.topic/1","content_sha256":"7a234962971fecf15a10edffff7a98f8cf5a7464712aa2f2b613f37e886c2d28","created":"2026-10-03T07:17:52Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":[],"salt":"7481c9cf03f4c67a5f3abef5250a0c9f5b2d8de630f912642e491415303859c6","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"topic"},"content":{"external_id":"hep.strong-cp","field":"hep","n":"1","review_cite":"L. Di Luzio, M. Giannotti, E. Nardi, L. Visinelli, The landscape of QCD axion models, Physics Reports, 2020","review_link":"https://doi.org/10.1016/j.physrep.2020.06.002","review_verified":"true","summary":"The theory of the strong force allows an angle $\\theta$ that would make the neutron a tiny electric dipole, but experiments find theta below one ten-billionth. A hypothetical light particle called the axion could explain this.","title":"Strong CP problem and the QCD axion","topic_ref":null,"why":"It is a fine-tuning puzzle in the tested part of the SM, and its favored solution predicts a new particle."},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"417555880359201cc195a916f3b947e690164dade4e3ac924d6e5d98d0f88eb7","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"3eb71bd4c9963b5ebec9fe043795c0c53c39b7dcf06d197bbad045b5f40dc3ce","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"5FyYd1BKWZNqrsYOj_GO1WTeF2R2q_dJNzKu3fzz9TmoSDlXiNkiWChuaFerdADLLvoy91zEpy92GqfpUD7vDw"},"schema":"pubphys.envelope/1"},"record_hash":"417555880359201cc195a916f3b947e690164dade4e3ac924d6e5d98d0f88eb7","leaf_index":251}