Long-Lived Giant Number Fluctuations in a Swarming Granular Nematic

By V. Narayan, S. Ramaswamy, Narayanan Menon. Science, 2006

703 citations recorded by the source corpus.

Coherently moving flocks of birds, beasts, or bacteria are examples of living matter with spontaneous orientational order. How do these systems differ from thermal equilibrium systems with such liquid crystalline order? Working with a fluidized monolayer of macroscopic rods in the nematic liquid crystalline phase, we find giant number fluctuations consistent with a standard deviation growing linearly with the mean, in contrast to any situation where the central limit theorem applies. These fluctuations are long-lived, decaying only as a logarithmic function of time. This shows that flocking, coherent motion, and large-scale inhomogeneity can appear in a system in which particles do not communicate except by contact.

Subfields: Computer Networks and Communications, Condensed Matter Physics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/10b49afa18ff2d5fa01a948e7915206f313a58f9

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Citations in the corpus

Meso-scale turbulence in living fluids (2012, background): “As evident from the inset, local density fluctuations that are important in the swarming/flocking regime (48, 49, 51) become suppressed at very high filling fractions (SI Appendix, Fig.”
Active Particles in Complex and Crowded Environments (2016, background): “…(Sanchez et al., 2012; Schaller et al., 2010; Sumino et al., 2012), to topological defects in nematic vesicles (Keber et al., 2014), vortices in active nematics (Giomi, 2015), agitated granular matter (Narayan et al., 2007), and schools of fish and flocks of birds (Vicsek and Zafeiris, 2012).”
A phase diagram for bacterial swarming (2019, background): “…active matter systems, including swimming (not swarming) bacteria in bulk or thin films [Sokolov 2007; Sokolov 2012], driven inanimate particles [Narayan 2007; Bricard 2013] or most models of self-propelled particles (SPPs), either discrete or continuous [e.g. Wensink 2012; Abkenar 2013;…”
Tuned, driven, and active soft matter (2015, background): “large number fluctuations were also observed in experiments [364, 366, 367].”
Temperature in and out of equilibrium: A review of concepts, tools and attempts (2017, background): “This makes active systems very interesting for the study of fluctuations, which are rarely negligible [295,296].”
Collective motion and density fluctuations in bacterial colonies (2010, background): “For higher density (Ntotal 1⁄4 718), the data show anomalous density fluctuations, sometimes called giant number fluctuations (7, 13).”
Symmetry, Thermodynamics, and Topology in Active Matter (2021, background): “[18] Vijay Narayan, Sriram Ramaswamy, and Narayanan Menon, “Long-lived giant number fluctuations in a swarming granular nematic,” Science 317, 105–108 (2007).”
Hydrodynamics of soft active matter (2013, methodology): “‘‘Giant density fluctuations’’ have now been seen experimentally in both polar and apolar vibrated granular matter, with reported measured values of the exponent a of 2apolar ¼ 1:45* 0:05 (Deseigne, Dauchot, and Chaté, 2010) and aapolar ' 1 (Narayan, Ramaswamy, and Menon, 2007).”
The statistical physics of active matter: From self-catalytic colloids to living cells (2017, background): “These fluctuations are quantified in numerical simulations from the structure factor at small wavenumber, and they have also been reported in experimental realizations of active ordered state [62,77].”
Topological active matter (2020, background): “Moreover, the resulting topological defects can move by themselves, that is, even in the absence of external forces or fields 7,41,42 .”
Pressure is not a state function for generic active fluids (2014, background): “This is true of many active systems, such as crawling cells [29], vibrated disks or grains [9, 10, 30], and colloidal rollers [22] or sliders [21].”