Controlling Inter-Particle Distances in Crowds of Motile, Cognitive, Active Particles

Abstract

Distance control in many-particle systems is a fundamental problem in nature. This becomes particularly relevant in systems of active agents, which can sense their environment and react by adjusting their direction of motion. We employ agent-based simulations to investigate the complex interplay between agent activity, characterized by P{\'e}clet number $Pe$, reorientation maneuverability $\Omega$, vision angle $\theta$ and vision range $R_0$, and agent density, which determines agent distancing and dynamics. We focus on semi-dense crowds, where the vision range is much larger than the particle size. The minimal distance to the nearest neighbors, exposure time, and persistence of orientation direction are analyzed to characterize the behavior. With increasing particle speed at fixed maneuverability, particles approach each other more closely, and exhibit shorter exposure times. The temporal persistence of motion decreases with increasing $Pe$, reflecting the impact of activity and maneuverability on direction changes. For a vision angle $\theta=\pi/4$, we observe the emergence of flocking aggregates with a band-like structure, reminiscent of the Viscek model. Additionally, for vision angles $\theta\ge \pi/2$, several quantities are found to display a universal scaling behavior with scaling variable $Pe^{3/2}/\Omega$. Our results are in good agreement with recent experiments of pedestrians in confined spaces.