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Nonequilibrium fluctuation relation for sheared micellar gel in a jammed state
1Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Physical Review Letters
|September 4, 2008
Summary
Micellar gels in a jammed state show fluctuating shear rates. A new effective temperature, linked to structural constraints, was determined using fluctuation relations and varies with system size.
Area of Science:
- Soft Matter Physics
- Rheology
- Statistical Mechanics
Background:
- Jammed states in soft materials like micellar gels exhibit complex flow behaviors.
- Understanding these behaviors is crucial for predicting material properties under stress.
Purpose of the Study:
- To investigate shear rate fluctuations in jammed micellar gels.
- To explore the applicability of steady-state fluctuation relations.
- To determine an effective temperature characterizing the jammed state's structural constraints.
Main Methods:
- Applying a fixed shear stress to a micellar gel in a jammed state.
- Analyzing the probability distribution functions of global power flux.
- Utilizing the Gallavotti-Cohen steady-state fluctuation relation.
- Measuring the stress dependence of effective temperature.
Main Results:
- Observed large, fluctuating shear rates (positive and negative) with a positive mean.
- Probability distributions of power flux ranged from Gaussian to non-Gaussian, matching fluctuation relation predictions.
- Determined an effective temperature related to structural constraints.
- Found that effective temperature and shear-rate fluctuation standard deviation increase as system size decreases.
Conclusions:
- The Gallavotti-Cohen steady-state fluctuation relation accurately describes the behavior of jammed micellar gels.
- An effective temperature can quantify the structural constraints of jammed states.
- System size significantly influences both effective temperature and shear rate fluctuations in these materials.
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