Master defense by Salik Ahmad Sultan

Activity-induced Patterns in Active Matter

Abstract: The spontaneous emergence of collective flows is a generic property of active fluids and often leads to chaotic flow patterns characterised by swirls, jets, and topological disclinations in their orientation field.

The main part of this thesis will explore a newly introduced active stabilising term to tame otherwise chaotic, active flows, showing how a balance between activity-induced order and disorder can act as a robust way of controlling and guiding active particles into dynamically ordered coherent structures. Here we find that the introduced term does stabilize active systems.

Furthermore, we uncover a range of new exotic phases where topological defects self-organise into chains and aster-like structures. Additionally, we extend this framework to a discrete phase-field model of a cell monolayer by characterising the impact of chiral active stresses acting in between the cells. Here we explore the emergence of chiral edge currents and coherent patterns of motion of the cells in different configurations of confined geometry.