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Evidence of fluctuation-induced first-order phase transition in active matter

ORAL

Abstract

In Vicsek-like active matter systems the interplay between density fluctuations and ferromagnetic/imitation interactions gives rise to a rich phenomenology. In particular, the ordering transition to the flocking state seems to be similar to a first-order phase transition. Intuitively this happens because of the positive feedback between density fluctuations and ferromagnetic interaction, however, a theoretical explanation is still missing. We address this problem by studying the Malthusian Toner-Tu theory (MTT) in its near-ordering phase. Because of the birth/death process, characteristic of this Malthusian model, density fluctuations are partially suppressed but still strong enough to give rise to a non-trivial phenomenology. We study the MTT model with perturbative renormalization group techniques. A one-loop calculation shows that the renormalization group flow drives the system in an unstable region, suggesting a fluctuation-induced first-order phase transition. This calculation could provide a rigorous explanation of why the disorder/order transition is first order in active matter systems.

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Presenters

  • Luca Di Carlo

    Princeton university

Authors

  • Luca Di Carlo

    Princeton university