{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"be534fccaa128a234cd6f92fb85dae54ac405367de071140a80e7b6061e0eeaa","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"ee4eaed2201e71080a3b4322ce1f852a531f96411f1899e0a756daecfd6a6f99","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"cosmo.cosmic-dawn.21cm-power-spectrum","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Radio arrays try to map how the hydrogen 21-cm signal varies from place to place in the early universe. Bright radio emission from our own galaxy is about 100,000 times stronger and must be removed.","posed_since":"","precise":"Detect the dimensionless 21-cm power spectrum $\\Delta^2_{21}(k, z)$ at $k \\sim 0.1 \\text{ to } 0.5\\,h/\\mathrm{Mpc}$ for $z = 6 \\text{ to } 25$, separating Galactic and extragalactic foregrounds. An answer is a detection with signal-to-noise above 5 in at least one redshift bin, giving the timing of X-ray heating and reionization.","problem_ref":null,"references":"","settled_by":"HERA full-array or SKA-Low power-spectrum detection confirmed by an independent array.","status_note":"HERA Phase I (2022) and Phase II (2025) set upper limits without a detection.","title":"What is the 21-cm fluctuation power during cosmic dawn and reionization?","topic_ref":"ea80801fd2eb5823d48bafd35c2c50fca035f01f2b6b883d55c93bfc64efc2da"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"b504274671f08405892d3abfb2f83ab49bbbcce0a39c500fb63667db38b85026","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"749d3c316544ccedb7657cf097c8eeb04c394ef695e462f42bb40daf236dbcfd","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"efP2qwln7WlOSDqR4J-IaM8NMVApz17AIS7_Rz-9XqXn3w0JisvFf3xUGg6NbAgUEAyqRI6p2-4ixQlpuRmTBw"},"schema":"pubphys.envelope/1"},"record_hash":"b504274671f08405892d3abfb2f83ab49bbbcce0a39c500fb63667db38b85026","leaf_index":1228}