{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"df0ce3b9b7d912ad5f730516d1c0f4823931fcd5a994f47d179967a0d7febf3b","created":"2026-10-03T07:17:53Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"b1824fcfde51d92206073dde1f8d3f49fe25f1d6b5be4105d878ce9809413051","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"amo.lorentz-cpt.antihydrogen-1s2s","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Antihydrogen (an antiproton bound to a positron) should have exactly the same energy levels as hydrogen if matter and antimatter mirror each other perfectly. The main ultraviolet line has been compared to a few parts in $10^{12}$; hydrogen itself is known about a thousand times better.","posed_since":"","precise":"ALPHA measured the antihydrogen $1\\mathrm{S}-2\\mathrm{S}$ two-photon frequency in agreement with hydrogen at about 2e-12 relative precision (2018). Determine whether nu_1S2S(Hbar) - nu_1S2S(H) is nonzero at the 1e-15 level, approaching the hydrogen precision of about 4e-15.","problem_ref":null,"references":"","settled_by":"Antihydrogen 1S-2S spectroscopy with laser-cooled, magnetically trapped atoms reaching sub-kHz resolution and 1e-15 accuracy.","status_note":"ALPHA demonstrated laser cooling of antihydrogen in 2021, a prerequisite for the next precision step.","title":"Does antihydrogen 1S-2S match hydrogen at 1e-15?","topic_ref":"a6fc573c8db5bce913b8300d4956b1137cedf47b39c553b8063ed7baf3f179b3"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d32c3b2077e2ce6a0db88d006adece91cf6fed11603e69ad3b1fc261cca48df4","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"dafd0198e7713fc0a1948205a9d9e081db6d8abec5f6b9f10e2fe6f272372a87","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ymaK-BNSYAtQ7zIJZ4sRXds7PUSWCXWoR3WByCiUNfUnTW1Yvc02dnPxol978SpEzri8p-Dd4ciwhce9s90fBQ"},"schema":"pubphys.envelope/1"},"record_hash":"d32c3b2077e2ce6a0db88d006adece91cf6fed11603e69ad3b1fc261cca48df4","leaf_index":418}