{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"1d7d1e95b97ed52c24c1e7a585e2d75e88f243379289f96d7c6606c15f199a73","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"00de42282976c3217e986aa4308dfe4a8c6d88d44e00cea2c68243dc3c1f935c","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.collective-behavior.scale-free-correlations","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"In starling flocks, a change in one bird's flight is correlated with birds across the whole flock, however large it is. Whether flocks are tuned to a special critical state to achieve this, and how, is debated.","posed_since":"2010","precise":"In wild starling flocks ($10^2\\text{ to }10^4$ birds), connected correlation functions of velocity fluctuations have correlation length $\\xi$ proportional to flock size $L$, for both orientation and speed (Cavagna and co-workers, 2010). Orientation correlations follow from Goldstone modes of broken rotational symmetry; speed correlations require tuning near a critical point or another mechanism. Determine the mechanism for scale-free speed correlations and whether it involves tuning.","problem_ref":null,"references":"","settled_by":"A model with independently inferred interaction parameters that reproduces $\\xi$ proportional to $L$ for speed across flock sizes, with or without tuning to a critical point.","status_note":"","title":"Why speed correlations in starling flocks are scale-free","topic_ref":"169c237bb7dec2b851fb7b715df607d983a88bff09590a878223e10c99e9ed50"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"ba7cb7f83c93b217eaa06a0ce13ae74648d31556e3786be7a7eb47429fe62161","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"71875f8f53e9a5e27f62b9d11fcde91e3cd5f30061e26406dd3653dd4836e111","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"FWw2-RzRi5xNS4P95fsJbdSmsOXqg_PMmN6PpqM2oTodRuG6Fv3YFuFUPksy3vftvv1140ZVbkzqDOIf1qpHAQ"},"schema":"pubphys.envelope/1"},"record_hash":"ba7cb7f83c93b217eaa06a0ce13ae74648d31556e3786be7a7eb47429fe62161","leaf_index":747}