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Defect Unbinding in Active Nematics.

Suraj Shankar1,2, Sriram Ramaswamy2,3, M Cristina Marchetti1,2

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This summary is machine-generated.

We reveal how activity influences topological defects in active nematic phases. Increased activity can lower the transition temperature, potentially disordering the system, while rotational noise stabilizes the nematic state.

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Area of Science:

  • Physics
  • Soft Matter Physics
  • Statistical Mechanics

Background:

  • Active nematic phases exhibit topological defects.
  • Nonequilibrium drive leads to spontaneous motility of +1/2 disclinations.

Purpose of the Study:

  • To formulate the statistical dynamics of topological defects in 2D active nematic phases.
  • To investigate the influence of activity on defect unbinding and phase transitions.

Main Methods:

  • Derivation of an interacting particle description for defects from hydrodynamic equations.
  • Analysis using perturbation theory to study the temperature-activity phase diagram.

Main Results:

  • Activity lowers the defect-unbinding transition temperature, defining a critical line.
  • Below a critical activity, rotational noise stabilizes the nematic state; this threshold vanishes at low temperatures (reentrant transition).
  • At high activity, active forces dominate, suggesting system disordering.

Conclusions:

  • The study provides a framework for understanding defect dynamics in active matter.
  • Rotational diffusion's 2D nature is crucial and cannot be simplified to 1D models.
  • Activity plays a complex role in stabilizing or destabilizing nematic order.