{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6a7e4beb7b7c4d57eced608cdde3afbbfdfa592d6dad09ebfe223e22948a1e75","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","d32c3b2077e2ce6a0db88d006adece91cf6fed11603e69ad3b1fc261cca48df4"],"salt":"eee32086c9808a476a81c77d9f65f8d02e6a9b2cbbd1ccab4ba90f4a36767100","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":"2","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 $2 \\times 10^{-12}$ relative precision (2018). Determine whether nu_1S2S(Hbar) - nu_1S2S(H) is nonzero at the $10^{-15}$ level, approaching the hydrogen precision of about 4e-15.","problem_ref":"d32c3b2077e2ce6a0db88d006adece91cf6fed11603e69ad3b1fc261cca48df4","references":"","settled_by":"Antihydrogen 1S-2S spectroscopy with laser-cooled, magnetically trapped atoms reaching sub-kHz resolution and $10^{-15}$ 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 $10^{-15}$?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"738e0edf2ab44076d72567c71692b71bd8adeae1031d1e2b4d1b8be9ae7b90bd","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"0bfe43d5ea17c828800f5010a4a23dd802e3296476bc06d526d7c946745b794b","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"loAyT98kMFUsueTL3QJUjCasrwhiKfp2Wu3iwQnDfrIWl4zC69K1vaUCK5h-jmlmQi7vZYjlNFTqwLXkNANyBQ"},"schema":"pubphys.envelope/1"},"record_hash":"738e0edf2ab44076d72567c71692b71bd8adeae1031d1e2b4d1b8be9ae7b90bd","leaf_index":2238}