Dipartimento di Fisica, Università di Bari, Italia
The collective behavior of an ensemble of self-propelled dumbbells described by Langevin equations with soft-core repulsive potential is considered. Self-propulsion is represented by a constant active force instantaneously directed along the major axis of each dumbbell. Even without attractive interaction, self-propulsion is shown to induce aggregation. At sufficient low temperatures the system separates into a dense phase with very compact clusters and a dilute phase. The phase diagram is studied for different Peclet numbers and packing fractions. The coarse-grained velocity field is random in the disordered region while shows coherent behavior below the critical temperature. The vorticity field is also calculated.
The presence of confined geometries has been also considered. For parameters corresponding to bulk disordered behavior, the system shows aggregation in proximity of the walls.