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Entropic effects in a nonequilibrium system: Flocks of birds

Author(s): Castellana, Michele; Bialek, William; Cavagna, Andrea; Giardina, Irene

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Abstract: When European starlings come together to form a flock, the distribution of their individual velocities narrows around the mean velocity of the flock. We argue that, in a broad class of models for the joint distribution of positions and velocities, this narrowing generates an entropic effect that opposes the cohesion of the flock. The strength of this effect depends strongly on the nature of the interactions among birds: If birds are coupled to a fixed number of neighbors, the entropic forces are weak, while if they couple to all other birds within a fixed distance, the entropic effects are sufficient to tear a flock apart.
Publication Date: May-2016
Electronic Publication Date: 23-May-2016
Citation: Castellana, Michele, Bialek, William, Cavagna, Andrea, Giardina, Irene. (2016). Entropic effects in a nonequilibrium system: Flocks of birds. Physical Review E, 93 (5), 10.1103/PhysRevE.93.052416
DOI: doi:10.1103/PhysRevE.93.052416
ISSN: 2470-0045
EISSN: 2470-0053
Pages: 052416
Type of Material: Journal Article
Journal/Proceeding Title: Physical Review E
Version: Author's manuscript

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