Active matter is a rapidly growing field that has potential applications to biological systems from the organism scale to the sub-cellular level. A key outstanding question relevant e.g. to biological tissues remains the behaviour of active particle systems at high density. We perform a numerical study of a dense collection of self-propelled particles with soft repulsive interactions in two dimensions. In a first system with alignment, we observe a jammed phase at high density and low self-propulsion speed. The dynamics of this phase is controlled by the low-frequency modes of the underlying jammed packing. The non-aligning system was recently shown to exhibit active phase separation in two dimensions in the absence of any attractive interaction or breaking of the orientational symmetry. We construct a phase diagram in terms of activity and packing fraction and identify three distinct regimes: a homogeneous liquid with anomalous cluster size distribution, a phase-separated state both at high and at low density, and a frozen phase. Finally, I will briefly discuss two applications of this area: Active matter on a Sphere (with Rastko Sknepnek, Dundee), and Cellular Migration in the corneal epithelium (with Martin Collinson, Aberdeen).
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..