{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"69dcce328d7dddc9498be75e7336979bb24d38a1730154d6aeb8ed8b85ef7b66","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"739a36c8ca0e400a1a7e5b254244444c7f1f94e22176d5d2d1b76bb01aa378ce","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cosmo.lithium-problem.primordial-helium","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"The fraction of mass in helium after the Big Bang is predicted to about one part in a thousand. One survey of tiny star-forming galaxies found less helium than predicted, which could point to an asymmetry between neutrinos and antineutrinos.","posed_since":"2022","precise":"Standard BBN with the CMB baryon density gives helium mass fraction $Y_{p} \\sim 0.247$, while the EMPRESS survey of extremely metal-poor galaxies reported $Y_{p} \\sim 0.237$ (2022, moderate confidence on the exact value), interpretable as an electron-neutrino chemical potential $\\xi_{e} \\sim 0.05$. Determine $Y_{p}$ with uncertainty below 0.003 from emission-line galaxies and CMB damping tails and state whether it agrees with standard BBN.","problem_ref":null,"references":"","settled_by":"Larger samples of metal-poor galaxies with near-infrared helium lines plus CMB-S4-class measurement of $Y_{p}$.","status_note":"","title":"Is the primordial helium abundance consistent with standard nucleosynthesis?","topic_ref":"3b29f7c24689f116d4e24a9b9965296a8a7d4d58f92b9ab5ac13f314c66ba629"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"439cefc9fcc976b7d7fe394881e7115000fe0899e51b76af0be56be7513ba431","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"f1b11a245dbfaf0d4fa4fbc73e4b02b00a3fede8fcb5ee098d0919eb2355b599","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"9GP8X7lcTIOYSx9vudJgthYuqmlRXQ9--kZ2z-ypWnTBESuwBaBhMdECAivlv-qa3GtrUDs_u_q9jxa3fEK6Bw"},"schema":"pubphys.envelope/1"},"record_hash":"439cefc9fcc976b7d7fe394881e7115000fe0899e51b76af0be56be7513ba431","leaf_index":1266}