Large-scale chaos and fluctuations in active nematics

Area of Science:

• Physics of complex systems
• Non-equilibrium statistical mechanics
• Soft matter physics

Background:

• Active nematics are systems of self-propelled or interacting anisotropic units.
• Dry granular systems offer a tunable platform to study active matter phenomena.
• Spatiotemporal chaos is a complex dynamic behavior observed in many physical systems.

Purpose of the Study:

• To investigate the emergence of large-scale spatiotemporal chaos in dry active nematics.
• To identify the underlying mechanisms driving chaotic dynamics in these systems.
• To characterize number fluctuations in both chaotic and ordered phases.

Main Methods:

• Analysis of deterministic hydrodynamic equations for active nematics.
• Study of the underlying self-propelled particle model.
• Investigation of band solutions and their stability.
• Characterization of density segregation and number fluctuations.

Main Results:

• Dry active nematics exhibit large-scale spatiotemporal chaos composed of interacting dense, ordered bands.
• Chaos originates from the generic instability of band solutions in the hydrodynamic equations.
• Giant number fluctuations in the chaotic phase are linked to density segregation.
• Anomalous, curvature-driven number fluctuations with a nontrivial scaling exponent are found in the quasi-ordered nematic phase.

Conclusions:

• The study elucidates the origin of spatiotemporal chaos in dry active nematics.
• It distinguishes between trivial fluctuations due to density segregation and anomalous fluctuations in ordered phases.
• The findings contribute to understanding complex dynamics in active matter systems.