Aggregation of foraging swarms
  In this paper we consider a continuous-time anisotropic swarm model with an attraction/repulsion function and study its aggregation properties. It is shown that the swarm members will aggregate and eventually form a cohesive cluster of finite size around the swarm center. We also study the swarm cohesiveness when the motion of each agent is a combination of the inter-individual interactions and the interaction of the agent with external environment. Moreover, we extend our results to more general attraction/repulsion functions. The model in this paper is more general than isotropic swarms and our results provide further insight into the effect of the interaction pattern on individual motion in a swarm system. 
Long Wang