{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"0d3ca3d73d5dbca6898a6419003f536f0542309baee1ea2afe3bd080d622b098","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"a73bd9201ca5b4b9d34f0f2e9fa1a3abf8baf24f634869b8d5dd618d37e7f56f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"bio.collective-behavior.swarm-dynamic-exponent","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"In midge swarms, the time over which fluctuations die out grows with the correlation length according to a power set by one number, the dynamic exponent. Its measured value, about 1.4, differs from standard theories of moving groups.","posed_since":"2017","precise":"In wild midge swarms the relaxation time of velocity fluctuations scales as $\\tau \\sim \\xi^z$ with measured $z = 1.37 \\pm 0.11$ (Cavagna and co-workers, 2023; $1.12 \\pm 0.16$ in the 2017 analysis), below $z = 2$ for overdamped dynamics. Determine the universality class: compute z in a field theory with inertial, spin-like velocity coupling and self-propulsion, and check it with the measured static and dynamic exponents.","problem_ref":null,"references":"","settled_by":"A renormalization-group value of z consistent with measurements on independent swarm data sets, together with matching static exponents.","status_note":"A 2023 renormalization-group calculation for an active inertial model gave $z = 1.35$, matching the measured $1.37 \\pm 0.11$ (Nature Physics, doi 10.1038/s41567-023-02028-0); confirmation on independent swarm data and of the static exponents is open.","title":"Dynamic critical exponent of natural insect 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