The physics of high-density crowds

Communication and information transfer between human subjects give rise to social conventions, shared norms, collective motion, and other efficient self-organized phenomena. During mass events such as concerts, parades, sporting events, and pilgrimages, crowd density can become extremely high, causing the breakdown of conventional information transfer and the emergence of potentially deadly collective motions.
Taking inspiration from the physics of jammed granular materials, we were able to identify the physical mechanisms underlying such collective motions, e.g. density waves, observed at high density.
However, understanding the coupling between information transfer and movement in the extreme case presented by high-density crowds is still an open question, and, likely, a fundamental step in understanding the dangers arising at mass gatherings.

In this talk, I will present the fundamental results we obtained when using granular materials techniques to understand the emergence of injurious collective motions in crowds. Then, I will show how traditional models of information dynamics can be spatially embedded to analyze the breakdown of information transfer in high-density scenarios, and its relationship with collective motion.