Simulating Pedestrian Avoidance: The Humans vs Zombies Scenario

This study introduces a unique active matter system as an application of the pedestrian collision avoidance paradigm, that proposes dynamically adjusting the desired velocity. We present a fictitious human-zombie scenario set within a closed geometry, combining prey-predator behavior with a one-way contagion process that can transform prey into predators. The system demonstrates varied responses, in cases where agents have the same maximum speeds, a single zombie always catches a human, whereas two zombies never catch a single human. As the number of human agents increases, observables, such as the final fraction of zombie agents and total conversion times, exhibit a significant change in the system's behavior at intermediate density values. Most notably, there is evidence of a first-order phase transition when the mean population speed is analyzed as an order parameter.