{"paper":{"title":"Hamiltonian flocks: Time-Reversal Symmetry and its consequences","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Hamiltonian flocks obey a generalized time-reversal symmetry that produces a mixed fluctuation-dissipation theorem.","cross_cats":[],"primary_cat":"cond-mat.stat-mech","authors_text":"Leticia F. Cugliandolo, Mathias Casiulis","submitted_at":"2026-04-03T09:33:04Z","abstract_excerpt":"The fluctuation-dissipation theorem is a hallmark of equilibrium systems that stems from their time-reversal symmetry. In many non-equilibrium systems, in particular active ones, extensions and explicit violations of this theorem are used to assess their ''distance'' to equilibrium. In Hamiltonian flocks, conservative yet non-Galilean models of polar liquids, previous work reported collective motion without the activity that usually underlies it. In this paper, we show that this model obeys a generalized time-reversal symmetry that yields a fluctuation-dissipation theorem that mixes position a"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The model obeys a generalized time-reversal symmetry that yields a fluctuation-dissipation theorem that mixes position and polarity degrees of freedom. Due to the oddness of spin under time reversal, the system also obeys Onsager-Casimir reciprocity rather than standard Onsager relations.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The Hamiltonian flocks model is invariant under the specific generalized time-reversal operation defined by the authors, which relies on the conservative, non-Galilean structure of the model and the odd parity of polarity under that operation.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Hamiltonian flocks obey a generalized time-reversal symmetry that yields a mixed fluctuation-dissipation theorem and Onsager-Casimir reciprocity, while naive time reversal produces spurious entropy production.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Hamiltonian flocks obey a generalized time-reversal symmetry that produces a mixed fluctuation-dissipation theorem.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"909eb7863af77932aca0255ceb6224c9ebc054428c208cc9b6c1c887ec2ad35b"},"source":{"id":"2604.02914","kind":"arxiv","version":2},"verdict":{"id":"65e491aa-f694-47ac-8663-a59963010ce6","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-13T18:20:37.521129Z","strongest_claim":"The model obeys a generalized time-reversal symmetry that yields a fluctuation-dissipation theorem that mixes position and polarity degrees of freedom. Due to the oddness of spin under time reversal, the system also obeys Onsager-Casimir reciprocity rather than standard Onsager relations.","one_line_summary":"Hamiltonian flocks obey a generalized time-reversal symmetry that yields a mixed fluctuation-dissipation theorem and Onsager-Casimir reciprocity, while naive time reversal produces spurious entropy production.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The Hamiltonian flocks model is invariant under the specific generalized time-reversal operation defined by the authors, which relies on the conservative, non-Galilean structure of the model and the odd parity of polarity under that operation.","pith_extraction_headline":"Hamiltonian flocks obey a generalized time-reversal symmetry that produces a mixed fluctuation-dissipation theorem."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2604.02914/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":1,"snapshot_sha256":"d3b573128da48d4ef2709975b85e4f2fe853a200e6d32b8c084d76c87d6926cf"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}