Dresden 2026 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 5: Focus Session: Physics of Behavior (joint session SOE/DY)

DY 5.2: Talk

Monday, March 9, 2026, 10:00–10:15, GÖR/0226

Spin-Waves without Spin-Waves: A Case for Soliton Propagation in Starling Flocks — •Andrea Cavagna — Institute for Complex Systems, Rome, Italy

Collective turns in starling flocks propagate linearly with negligible attenuation, indicating the existence of an underdamped sector in the dispersion relation. Beside granting linear propagation of the phase perturbations, the real part of the frequency should also yield a spin-wave form of the unperturbed correlation function. However, new high-resolution experiments on real flocks show that underdamped traveling waves coexist with an overdamped Lorentzian correlation. Theory and experiments are reconciled once we add to the dynamics a Fermi-Pasta-Ulam-Tsingou term.

Keywords: active matter; collective behaviour; flocking