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Polarization-density patterns of active particles in motility gradients
Sven Auschra1, Viktor Holubec1,2, Nicola Andreas Söker3
1Institute for Theoretical Physics, Leipzig University, 04103 Leipzig, Germany.
Physical Review. E
|July 17, 2021
Summary
Active Brownian particle models explain how Janus-type swimmers align density and polarization in activity gradients. These findings, matching experimental data, advance understanding of active matter dynamics.
Area of Science:
- Physics
- Soft Matter Physics
- Statistical Mechanics
Background:
- Motile active matter exhibits emergent phenomena like density modulations and particle polarization, especially in activity gradients.
- Janus-type swimmers are model systems for active matter, displaying complex behaviors.
Purpose of the Study:
- To derive analytical expressions for density and polarization profiles of a single Janus-type swimmer near an activity step.
- To investigate the role of orientation-dependent propulsion speed in active matter dynamics.
Main Methods:
- Employing the active-Brownian-particle model for theoretical analysis.
- Deriving precise analytical expressions for swimmer profiles.
- Utilizing a schematic two-species "run-and-tumble" model for conceptual elucidation.
Main Results:
- Precise analytical expressions for density and polarization profiles were obtained.
- Results show good agreement with experimental data for thermophoretic microswimmers.
- The model accommodates optional orientation-dependent propulsion speeds.
Conclusions:
- The active-Brownian-particle model accurately describes colocalization of density and polarization in active matter systems.
- Findings provide a template for studying motility-induced phase separation and boundary effects.
- The underlying physics is robustly captured by simplified models.
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