Emergent correlations, oscillations and order in active solids

Speaker: Silke Henkes (Leiden University)

Abstract:

Active materials, such as birds, cells, and active colloids are quite well understood at low density through the theories of active liquids. However, active solids are very different and barely understood at this point. I will first show that there is a very generic mechanism of generating correlations in active solids where the persistence of polar active driving interacts with overdamped elasticity. This effect appears in many systems, and I will show recent work on strings of active colloids, as well as epithelial tissues and their boundaries. Adding a coupling with a particles’ own velocity to this leads to a striking oscillating state in confinement, recently demonstrated in engineered oscillators, tissues, and even human crowds. Finally, changing the driving to active fluctuating stresses, instead of forces, changes the physics drastically: instead of mesoscale correlations, long wavelength modes are damped. This then leads to long range translational order in two dimensions, and hyperuniformity.

This seminar will take place in room C3.158