“…In many biological applications the number of interacting particles is large and one may consider the underlying continuum formulation of (1.1), which is known as the aggregation equation [9,11,42] and of the form ρ t + ∇ · (ρu) = 0, u = −∇W * ρ, (1.2) where u = u(t, x) is the macroscopic velocity field and ρ = ρ(t, x) denotes the density of particles at location x ∈ R n at time t > 0. The aggregation equation (1.2) has been studied extensively recently, mainly in terms of its gradient flow structure [2,29,30,44,54], the blow-up dynamics for fully attractive potentials [9,10,21,28], and the rich variety of steady states for repulsiveattractive potentials [3,4,5,8,10,19,20,22,23,38,39,50,55,56,27,26,31]. In biological applications, the interactions determined by the force F , or equivalently the interaction potential W , are usually described by short-range repulsion, preventing collisions between the individuals, as well as long-range attraction, keeping the swarm cohesive [46,47].…”