{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"307baa3dc1c065e19ff21e59bc6036f4fd9b8f9a9c491d491f34ffe86fbc3ed5","created":"2026-10-03T07:17:53Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"823ee164305c2ee82c46e3a876be78ac20e78a6fe299c51f1626f1d5f242d91f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"amo.efimov-universality.three-body-parameter","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"The position of the first Efimov molecule is measured by a number (the three-body parameter), found to be close to 9.7 times a basic atomic length. The task is a theory that predicts it for every atom and resonance, including narrow ones.","posed_since":"2011","precise":"For identical bosons near an isolated s-wave Feshbach resonance with van der Waals length $r_{\\mathrm{vdW}}$, resonance strength $s_{\\mathrm{res}}$ and background scattering length $a_{\\mathrm{bg}}$, predict a_-^(1)/r_vdW, the scattering length of the first three-body loss resonance. Answer: a model reproducing all measured values (Cs, K-39, Li-7, Rb-85) within experimental error, including the deviation from -9.7 for $s_{\\mathrm{res}} < 1$.","problem_ref":null,"references":"","settled_by":"A multichannel three-body calculation that matches every measured a_-^(1) within error bars, plus a new measurement at a narrow resonance that it predicts in advance.","status_note":"Theory traced the value to a universal three-body barrier near $R \\sim 2 r_{\\mathrm{vdW}}$ (Wang et al., PRL 2012), but measurements at resonances of different widths scatter by roughly 15 to 30% around the universal value.","title":"Predicting the three-body parameter across Feshbach resonances of any width","topic_ref":"339b6d63b4f6e3414be07628eacf49cfd6937fceb21d43c10a8b4202c093ede0"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"b962fefc800c401b1acedf5a869815647d5146d2ee562d18e3d5f83bcc07ba1c","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"dfb9ee18d088d84b50495a776c3bc24d89419d93e1cf79439d4b30ea42018c3e","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"C03n3CHOtIlUpt-oSrjWFpdSCbVlr0Whh9AT6nlh71XVT4BnInWweM2EwGna0qlgs4jrdK-3oQpYNU2ggzaODQ"},"schema":"pubphys.envelope/1"},"record_hash":"b962fefc800c401b1acedf5a869815647d5146d2ee562d18e3d5f83bcc07ba1c","leaf_index":404}