Noise-Induced Transition from Translational to Rotational Motion of   Swarms
  We consider a model of active Brownian agents interacting via a harmonic attractive potential in a two-dimensional system in the presence of noise. By numerical simulations, we show that this model possesses a noise-induced transition characterized by the breakdown of translational motion and the onset of swarm rotation as the noise intensity is increased. Statistical properties of swarm dynamics in the weak noise limit are further analytically investigated. 
Udo Erdmann, Werner Ebeling, Alexander S. Mikhailov