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Symmetry-reversals in chiral active matter
Marcel Workamp1, Gustavo Ramirez, Karen E Daniels
1Physical Chemistry and Soft Matter, Wageningen University & Research, Wageningen, The Netherlands. joshua.dijksman@wur.nl.
Soft Matter
|June 7, 2018
Summary
Active granular disks transition circulation direction with packing density. Their velocity distributions are Gaussian, and a temperature-like parameter universally predicts collective behavior, highlighting geometric friction
Area of Science:
- Active matter physics
- Granular materials science
- Non-equilibrium statistical mechanics
Background:
- Active granular materials exhibit complex collective behaviors.
- Interparticle interactions significantly influence system dynamics.
- Geometric friction from particle shape can mediate interactions.
Purpose of the Study:
- To investigate the collective circulation and statistical properties of spinning disks in a confined granular system.
- To explore the role of packing fraction and geometric friction on emergent behaviors.
- To characterize the relationship between particle-level properties and macroscopic system dynamics.
Main Methods:
- Experimental study using individually-driven, spinning disks in a circular arena.
- Systematic variation of packing fraction (φ) to observe transitions.
- Analysis of particle velocity distributions and collective circulation rates.
- Fitting speed distributions to Maxwell-Boltzmann to derive a temperature-like parameter.
Main Results:
- Disks exhibit a transition in collective circulation direction (clockwise to counter-clockwise) with increasing packing fraction.
- Particle velocity distributions are consistently Gaussian across a wide range of packing fractions.
- A universal temperature-like parameter, directly related to mean translational energy, is identified as a function of packing fraction.
- Collective circulation rate and the ratio of orbital to spin kinetic energy show universal dependencies on packing fraction and geometric friction.
Conclusions:
- The collective behavior of active granular systems is strongly dependent on both the driving mechanism and interparticle interactions.
- Geometric friction plays a crucial role in mediating collective circulation and energy dynamics.
- The identified universal relationships provide a framework for understanding and predicting the behavior of such active matter systems.
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