Forces in Active Systems

Orateur : Yariv KAFRI (Department of Physics, Technion, Haifa, Israel)

The talk will discuss forces in active systems - a class of non-equilibrium systems. In recent years there has been much progress in understanding the forces exerted by active fluids on confining walls and on objects embedded in them. The talk will start by giving an overview of these results, including the lack of an equation of state for the pressure. Then I will show that when two bodies are placed in an active fluid generic long-range interactions between the bodies exist. They decay as a power law with the distance between the bodies, are anisotropic, and do not obey an action-reaction principle. The interactions lead to rich dynamics of the bodies, illustrated by the spontaneous synchronized rotation of pinned non-chiral bodies and the formation of traveling bound pairs. The occurrence of these phenomena depends on tunable properties of the bodies, thus opening new possibilities for self-assembly mediated by active fluids.

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