Out of equilibrium response and fluctuation-dissipation violations across scales in flocking systems

Fuente: arXiv
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Hauptverfasser: Ferretti, Federica, Giardina, Irene, Grigera, Tomas, Pisegna, Giulia, Veca, Mario
Format: Preprint
Veröffentlicht: 2024
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author Ferretti, Federica
Giardina, Irene
Grigera, Tomas
Pisegna, Giulia
Veca, Mario
author_facet Ferretti, Federica
Giardina, Irene
Grigera, Tomas
Pisegna, Giulia
Veca, Mario
contents Flocking systems are known to be strongly out of equilibrium. Energy input occurs at the individual level to ensure self-propulsion, and the individual motility in turn contributes to ordering, enhancing information propagation and strengthening collective motion. However, even beyond ordering, a crucial feature of natural aggregations is response. How, then, do off-equilibrium features affect the response of the system? In this work, we consider a minimal model of flocking and investigate response behavior under directional perturbations. We show that equilibrium dynamical fluctuation-dissipation relations between response and correlations are violated, both at the local and at the global level. The amount of violation peaks at the ordering transition, exactly as for the entropy production rate. Entropy is always produced locally and connected to the local fluctuation-dissipation violation via Harada-Sasa relationships. However, cooperative mechanisms close to the transition spread off-equilibrium effects to the whole system, producing an out of equilibrium response on the global scale. Our findings elucidate the role of activity and interactions in the cost repartition of collective behavior and explain what observed in experiments on natural living groups.
format Preprint
id arxiv_https___arxiv_org_abs_2405_12874
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Out of equilibrium response and fluctuation-dissipation violations across scales in flocking systems
Ferretti, Federica
Giardina, Irene
Grigera, Tomas
Pisegna, Giulia
Veca, Mario
Statistical Mechanics
Flocking systems are known to be strongly out of equilibrium. Energy input occurs at the individual level to ensure self-propulsion, and the individual motility in turn contributes to ordering, enhancing information propagation and strengthening collective motion. However, even beyond ordering, a crucial feature of natural aggregations is response. How, then, do off-equilibrium features affect the response of the system? In this work, we consider a minimal model of flocking and investigate response behavior under directional perturbations. We show that equilibrium dynamical fluctuation-dissipation relations between response and correlations are violated, both at the local and at the global level. The amount of violation peaks at the ordering transition, exactly as for the entropy production rate. Entropy is always produced locally and connected to the local fluctuation-dissipation violation via Harada-Sasa relationships. However, cooperative mechanisms close to the transition spread off-equilibrium effects to the whole system, producing an out of equilibrium response on the global scale. Our findings elucidate the role of activity and interactions in the cost repartition of collective behavior and explain what observed in experiments on natural living groups.
title Out of equilibrium response and fluctuation-dissipation violations across scales in flocking systems
topic Statistical Mechanics
url https://arxiv.org/abs/2405.12874