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Hidden order in active nematic defects.

Alexis de la Cotte1,2, Daniel J G Pearce3, Jyothishraj Nambisan1,2

  • 1Department of Condensed Matter Physics, University of Barcelona, Barcelona 08028, Spain.

Proceedings of the National Academy of Sciences of the United States of America
|September 29, 2025
PubMed
Summary
This summary is machine-generated.

Active nematic defects show suppressed fluctuations, exhibiting hidden order across scales. This hyperuniformity arises from activity, not thermal effects, revealing organization in disordered systems.

Keywords:
active matterhyperuniformitynematic defectsnumber fluctuations

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Area of Science:

  • Physics
  • Statistical Mechanics
  • Soft Matter Physics

Background:

  • Hyperuniformity and giant number fluctuations are key concepts in non-equilibrium systems.
  • Active matter is often characterized by large fluctuations, contrasting with hyperuniformity observed in ordered systems.

Purpose of the Study:

  • To investigate the statistical correlations in active nematic defects.
  • To determine if active nematic defects exhibit hyperuniformity or giant number fluctuations.
  • To elucidate the role of activity versus thermal fluctuations in defect organization.

Main Methods:

  • Modeling nematic defects using continuum densities.
  • Analyzing experimental findings.
  • Employing hydrodynamic theory and agent-based simulations.

Main Results:

  • Active nematic defects display suppressed fluctuations, akin to ordered lattices.
  • Hyperuniformity emerges in the limit of activity-driven proliferation, independent of thermal fluctuations.
  • A finite range of length scales characterizes hyperuniformity when both activity and thermal effects are present.
  • Subpopulations of positive or negative defects show enhanced organization, indicating a lack of multihyperuniformity.

Conclusions:

  • The disordered state of active nematic defects possesses hidden order across scales.
  • Activity-driven proliferation is crucial for achieving hyperuniformity in these systems.
  • The interplay between defect dynamics (creation/annihilation, repulsion/attraction) and external factors governs the emergent hyperuniform structure.