He is also known for the Kardar–Parisi–Zhang equation modelling stochastic aggregation. From the point of view of complex systems, he worked on the collective motion of animals (such as swarms and flocks).
The individual's work focuses on the Kardar–Parisi–Zhang equation, which models stochastic aggregation.  He has also researched the collective movement of animals like swarms and flocks from a complex systems perspective.