Séminaire du LPTMS : Giulia Pisegna (University of Rome La Sapienza)


11:00 - 12:00

LPTMS (100% online seminar)
LPTMS - Bâtiment Pascal n° 530 rue André Rivière - Université Paris-Saclay, Orsay, 91405

Type d’évènement

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Dynamical Renormalization Group Approach to the Collective Behavior of Swarms

Giulia Pisegna (University of Rome La Sapienza)

Online seminar — Zoom Meeting ID: 951 4623 4806 — Passcode: ask L. Mazza and D. Petrov —

We study the critical behavior of a model with nondissipative couplings aimed at describing the collective behavior of natural swarms, using the dynamical renormalization group under a fixed-network approximation. At one loop, we find a crossover between an unstable fixed point, characterized by a dynamical critical exponent z=d/2, and a stable fixed point with z=2, a result we confirm through numerical simulations. The crossover is regulated by a length scale given by the ratio between the transport coefficient and the effective friction, so that in finite-size biological systems with low dissipation, dynamics is ruled by the unstable fixed point. In three dimensions this mechanism gives z=3/2, a value significantly closer to the experimental window, 1.0≤z≤1.3, than the value z≈2 numerically found in fully dissipative models, either at or off equilibrium. This result indicates that nondissipative dynamical couplings are necessary to develop a theory of natural swarms fully consistent with experiments.

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