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DY: Fachverband Dynamik und Statistische Physik

DY 43: Active Matter IV (joint session DY/BP/CPP)

DY 43.3: Talk

Thursday, March 21, 2024, 10:15–10:30, BH-N 334

Emergent Metric-like States of Active Particles with Metric-free Polar Alignment — Yinong Zhao¹, Cristian L. Huepe², and •Pawel Romanczuk^3,4 — ¹Shanghai Jiao Tong University, Shanghai, PR China — ²Northwestern University, Chicago, USA — ³Department of Biology, Humboldt Universität zu Berlin, Germany — ⁴Excellence cluster "Science of Intelligence", Berlin

We study a model of self-propelled particles interacting with their k-nearest neighbors through polar alignment. By exploring its phase space as a function of two nondimensional parameters (scaled alignment strength g and Peclet number Pe), we identify two distinct order-disorder transitions. One appears to be continuous, occurs at a low critical g value independent of Pe, and resembles a mean-field transition with no density-order coupling. The other is discontinuous, depends on a combined control parameter involving g and Pe, and results from the formation of small, dense, highly persistent clusters of particles that follow metric-like dynamics. These dense clusters form at a critical value of the combined control parameter Pe/g^α , with α≈1.5, which appears to be valid for different alignment-based models. Our study shows that models of active particles with metric-free interactions can produce characteristic length-scales and self-organize into metric-like collective states that undergo metric-like transitions.

Keywords: active matter; alignment; collective movement; phase transition; flocking