Additivity and density fluctuations in Vicsek-like models of self-propelled particles

Subhadip Chakraborti; Punyabrata Pradhan

doi:10.1103/physreve.99.052604

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arXiv · 1812.05365

Additivity and density fluctuations in Vicsek-like models of self-propelled particles

Subhadip Chakraborti·Punyabrata Pradhan

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Abstract

We study coarse-grained density fluctuations in the disordered phase of the paradigmatic Vicsek-like models of self-propelled particles with alignment interactions and random self-propulsion velocities. By numerically integrating a fluctuation-response relation - the direct consequence of an additivity property, we compute logarithm of the large-deviation probabilities of the coarse-grained subsystem density, while the system is in the disordered fluid phase with vanishing macroscopic velocity. The large-deviation probabilities, computed within additivity, agree remarkably well with that obtained from direct microscopic simulations of the models. Our results provide an evidence of the existence of an equilibrium-like chemical potential, which governs the coarse-grained density fluctuations in the Vicsek-like models. Moreover, comparison of the particle-number fluctuations among several self-propelled particle systems suggests a common mechanism through which the number fluctuations arise in such systems.

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Subhadip Chakraborti, Punyabrata Pradhan. 2019-05-17. Additivity and density fluctuations in Vicsek-like models of self-propelled particles. https://doi.org/10.1103/physreve.99.052604

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