Hidden order in active nematic defects

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.