{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"960d8443c7dd3c8b950db448496faf7a3b85ee3e278e5219fac080586e665448","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["aae6a1ff99d44ce28f57912944d7e9b374bca3e3373a1f42ec8e05762624121a","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"5ca08e6ebc17dae088390c0dad8ae0ae2e71e7f45fc63f99259c81a315f7d3f9","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":["ai:gpt-5.5"],"external_id":"qi.measurement-problem.definite-outcomes","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"When a detector interacts with a particle in a superposition (a blend of states), the Schrodinger equation predicts a blended detector, yet one reading is always seen. The question is what physical process or rule selects that single reading.","posed_since":"","precise":"For a system $S$ in state $\\sum_{k} c_k |k>$ coupled unitarily to apparatus $A$ and environment $E$, unitary evolution gives $\\sum_{k} c_k |k>|A_k>|E_k>$; decoherence makes the reduced density matrix of $S+A$ diagonal but selects no single $k$. Required: a modified dynamics, an added ontology (hidden variables, branches) or a principled account that yields single outcomes with frequencies $\\mid c_k\\mid^2$, together with either predictions that differ from standard quantum mechanics or a proof of empirical equivalence. This is the root problem of the topic; its workable sharper forms are listed under related.","problem_ref":"aae6a1ff99d44ce28f57912944d7e9b374bca3e3373a1f42ec8e05762624121a","references":"","settled_by":"An experiment detecting a deviation from unitary evolution predicted by one class of proposals, or a proof that a specified account reproduces all quantum predictions using only its stated assumptions.","status_note":"","title":"Why does a measurement produce one definite outcome?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"2fafa01c35fa509751aa62abfaf12dbe58b4e5c771230fdfc31b795756eff527","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a0ff82d100d00a787dcd903bcb25d84fbaaffd3c2da1eccec9b93711488ad983","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"615ochZdgrBpx2HK0YDCzKaoe4ZBiGnlgUHT-QvJWBpoNzy4WRBof8etT4vgIk5AbhbtrCsMdsXKJAlR3fExCQ"},"schema":"pubphys.envelope/1"},"record_hash":"2fafa01c35fa509751aa62abfaf12dbe58b4e5c771230fdfc31b795756eff527","leaf_index":3730}