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Fluctuations and rheology in active bacterial suspensions
D T N Chen1, A W C Lau, L A Hough
1Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA.
Physical Review Letters
|October 13, 2007
Summary
This study reveals that active bacterial baths violate the fluctuation-dissipation theorem, offering insights into the power spectrum of bacterial stress fluctuations.
Area of Science:
- Physics of complex systems
- Soft matter physics
- Statistical mechanics
Background:
- Active matter systems, such as bacterial baths, exhibit unique nonequilibrium properties.
- Understanding these properties is crucial for fields ranging from biophysics to materials science.
Purpose of the Study:
- To investigate the nonequilibrium properties of an active bacterial bath.
- To examine the violation of the fluctuation-dissipation theorem in such systems.
- To characterize the active stress fluctuations within the bacterial bath.
Main Methods:
- Measurements of correlations between passive tracer particles.
- Analysis of the response function of a driven, optically trapped tracer.
- Development of a theoretical model for coupled bacterial fluctuations.
Main Results:
- Demonstrated violation of the fluctuation-dissipation theorem in the active bacterial bath.
- Successfully extracted the power spectrum of active stress fluctuations.
- Observed a 1/sqrt[omega] scaling in the noise spectrum under certain conditions.
Conclusions:
- The fluctuation-dissipation theorem is violated in active bacterial baths.
- The observed noise spectrum scaling can be explained by a theoretical model of coupled bacterial fluctuations.
- This work provides a framework for understanding nonequilibrium phenomena in active matter.
