| Abstract: | Cooperation is vital for the survival of a swarm. No single bird is faster than a jet plane, and no single fish is faster than a speed boat — humans beat individual animals in air, land, and sea. But, when animals cooperate and swarm, they beat us since biblical times. Inspired by non-equilibrium statistical physics I will shed light on cooperative behavior observed in the animal kingdom. I will present our recent experimental findings that generalize the dynamics of known active particles. The particles are characterized by a charge-like parameter that is empirically well-defined, has units of curvature, and stems from a mechanical description of a vibrating walker. Particles with a negative “active charge” are attracted to repulsive potentials, effectively going uphill. Some animals are known to go uphill, and the proposed force-alignment response suggests a bio-mechanical contribution to this widespread behavioral trait. Moreover, the force-alignment response leads to unique collective behavior — an ensemble of such active particles spontaneously displays cooperative transport. This allows particles to coordinate the movement of a much larger object without using any circuitry, sensors, or communication. We call such active particles “transportons”, and using both experiments and simulations, I will show that the transport propensity of a swarm of transporters is super-linear with group size, a hallmark of cooperation. |
