A physics team in Dresden has developed a new theory to describe nonreciprocal interactions within collective systems such as bird flocks and cells [1, 2].
This advancement allows scientists to create more accurate and efficient simulations of how groups move and interact when the influence between individuals is not mutual. Traditional models based on Newtonian physics often struggle with these specific dynamics, making the new framework essential for understanding complex biological and social movements.
The research was led by Roderich Moessner, a founding member of the Würzburg–Dresden Cluster of Excellence [1, 2]. The team focused on systems where interactions are nonreciprocal, meaning one entity may react to another without the second entity responding in kind. This phenomenon is common in the natural world, from the way birds maintain positions in a flock to the movement of bacteria [1, 2].
By moving beyond standard reciprocal models, the Dresden team can now better simulate a variety of collective behaviors. These include the flow of human crowds, and the organization of cellular structures [1, 2]. The theory provides a mathematical foundation that simplifies the computational requirements for these simulations, potentially reducing the time and power needed to model large-scale systems.
The work comes from the Würzburg–Dresden Cluster of Excellence in Germany [1, 2]. The team said the theory will be applied across multiple disciplines, bridging the gap between theoretical physics and observational biology.
“A new theory to describe nonreciprocal interactions within collective systems”
This theoretical shift addresses a fundamental gap in how science models 'active matter.' By accounting for nonreciprocal interactions, researchers can move away from the limitations of Newton's third law—which posits that every action has an equal and opposite reaction—to more accurately reflect how biological agents actually behave in the real world.
