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Long-lived Giant Number Fluctuations in a Swarming Granular Nematic

Vijay Narayan·Sriram Ramaswamy·Narayanan Menon
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Abstract

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.

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Vijay Narayan, Sriram Ramaswamy, Narayanan Menon. 2007-06-14. Long-lived Giant Number Fluctuations in a Swarming Granular Nematic. https://doi.org/10.1126/science.1140414

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