MPI-DS Colloquium: Bulk condensation by an active edge, and other stories in active granular mat-ter

My talk will present experiments and theory, supported by mechanically detailed simulations, on a childishly simple realisation of active matter. The system is a monolayer of millimetre-sized grains energised by vertical vibration. Depending on the (a)symmetries of their shape, these particles can self-propel, or partition their energy unequally between two directions of motion, or simply diffuse. After a summary of our early work on flocking and our recent studies on non-reciprocal elastic "taxis", I will present our latest findings on bulk condensation and sublimation of spherical beads by a tiny population of orientable motile grains, which we understand within the framework of a theory with a naturally non-reciprocal Cahn-Hilliard structure.