Dynamics of Topological Defects in Active Nematics

Statistical Physics and Complexity Group meeting

Dynamics of Topological Defects in Active Nematics

  • Event time: 3:00pm until 4:00pm
  • Event date: 26th October 2021
  • Speaker: (UC Santa Barbara)
  • Location: Zoom - see email invite.

Event details

Topological defects - singular tears of the order parameter field that cannot be removed by smooth deformations - are often formed in quenches from the disordered state or when order is frustrated by curvature, external fields or boundary conditions. In equilibrium two-dimensional systems, such as thin films of superfluids, crystals, liquid crystals and magnets, order-disorder transitions are controlled by defect unbinding described via the Berezinskii-Kosterlitz-Thouless mapping of the statistical physics of defects onto a Coulomb gas. In active liquid crystals, topological defects become motile particles and proliferate spontaneously in the state of self-sustained turbulent-like motion ubiquitously observed in these systems.

In this talk I will outline a framework for formulating the statistical physics of defects in active nematics as quasiparticles and show that by viewing the active nematic as a collection of swarming and interacting active defects, the onset of active turbulence can be described as an activity-driven defect unbinding transition. A hydrodynamic theory of the gas of unbound defects additonally captures states of hierarchically organized active matter and the role of activity gradients for confining defects and harnessing active flows.

Event resources