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Granger causality and cross recurrence plots in rheochaos
Rajesh Ganapathy1, Govindan Rangarajan, A K Sood
1Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Summary
This study reveals a feedback loop between stress and micelle orientation during relaxation. Micelle orientation significantly impacts stress, demonstrating coupled dynamics in wormlike micelles.
Area of Science:
- Soft Matter Physics
- Materials Science
- Rheology
Background:
- Wormlike micelles exhibit complex rheological behavior.
- Understanding the relationship between stress and micelle structure is crucial for materials science.
- Simultaneous measurement of stress and micelle orientation is challenging.
Purpose of the Study:
- To investigate the causal relationship between stress and micelle orientational ordering.
- To analyze the phase space dynamics of stress relaxation in wormlike micelles.
- To apply Granger causality and cross recurrence plots to rheological data.
Main Methods:
- Utilized a Rheo-SALS (rheology + small angle light scattering) apparatus.
- Performed stress relaxation measurements on wormlike micelles.
- Applied linear and nonlinear Granger causality analysis.
- Employed cross recurrence plots (CRPs) to study phase space dynamics.
Main Results:
- Identified a feedback mechanism between stress and depolarized intensity (micelle orientation).
- Found that micelle orientation has a stronger causal influence on stress than vice versa.
- Cross recurrence plots demonstrated shared phase space dynamics between stress and orientation.
Conclusions:
- The stress relaxation of wormlike micelles involves coupled dynamics between macroscopic stress and microscopic orientational order.
- Micelle orientation plays a dominant role in driving stress changes during relaxation.
- The findings provide new insights into the microrheology of soft materials.
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