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DY: Fachverband Dynamik und Statistische Physik
DY 30: Focus Session: New Trends in Nonequilibrium Physics – Conservation Laws and Nonreciprocal Interactions II
DY 30.4: Talk
Wednesday, March 20, 2024, 16:00–16:15, BH-N 243
Formation of trails and bands of signaling active particles — •Zahra Mokhtari1, Robert Grossmann2, Robert Patterson3, and Felix Höfling1,4 — 1Institut für Mathematik, Freie Universität Berlin — 2Institut für Physik und Astronomie, Universität Potsdam — 3WIAS Berlin — 4Zuse Institute Berlin
To shed light on pattern formation of active particles with nonreciprocal interactions, we study self-propelled agents that interact via self-generated fields: individual particles deposit traces of pheromones which encode their current walking direction, in turn influencing the direction of motion of passing agents. In contrast to direct binary alignment interactions, the communication via self-generated fields constitutes a type of time-delayed, non-reciprocal feedback. The system exhibits different stable patterns: the collective dynamics is of the Vicsek type in the limit of short-lived traces, thus forming transversely moving bands. For prolonged pheromone lifetime, particles are found to gather along macroscopic narrow trails along the direction of motion. To elucidate the transitions between these states, we derive hydrodynamic equations within a mean-field approximation, unraveling a nuanced phase diagram dependent on pheromone lifetime. Combining numerics and a linear stability analysis reveals that transversal bands are destabilized in favor of the emergence of *longitudinal* trails. Thereby, this work provides a first steps towards an understanding of the role of nonreciprocal, delayed feedback interactions for the symmetry and structure of a novel type of emergent patterns forming under nonequilibrium conditions.
Keywords: active matter; non-reciprocal interactions; non-equilibrium phase transitions; delayed feedback; coarse-graining techniques