“…These models include short-range repulsion, long-range attraction, self-propelling and friction forces, reorientation or alignment see [4,65,58,66,60,53,37,57,7,6]. We consider self-propelled particles with Rayleigh friction [35,34,27,32,8,3,30,31], and alignment, introduced through the Cucker-Smale reorientation procedure [38,39], see also [56,54,28,29,61,62] for further details and [59] for a survey. If we denote by f = f (t, x, v) ≥ 0 the particle density in the phase space (x, v) ∈ R d × R d , with d ∈ {2, 3}, the self-propulsion/friction mechanism is given by the term div v {f (α − β|v| 2 )v}.…”