Thursday January the 22nd at 11 am in PMC seminar room (Jean Mandel) :
Instances of self-propelled entities are many, ranging from bacteria and cells to active colloids or bird flocks. The physics of these systems raises a variety of questions, ranging from the propulsion mechanism and the properties of individual trajectories to the collective effects resulting from interactions. I will present two case studies involving such active motion. The first study aims to theoretically characterize the random walks of swimming bacteria in both bulk and porous habitats. In the latter case, we find a universal law of dispersal. The second study describes a collective effect observed in recent experiments where motile cells spontaneously self-assemble into compact domains. We demonstrate that the underlying mechanism is microphase separation, long known in polymeric materials, but never observed so far in living cells.