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The influence of diffusing diffusivity on barrier crossing dynamics
1Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India.
The Journal of Chemical Physics
|July 14, 2026
Summary
This study explores how "diffusing diffusivity" alters condensed phase reaction dynamics. It reveals that this mechanism introduces dynamic heterogeneity in barrier crossing statistics, differing from traditional models.
Area of Science:
- Chemical Physics
- Statistical Mechanics
- Biophysics
Background:
- Conventional condensed phase reaction dynamics often rely on Kramers' flux-over-population approach.
- Anomalous particle behavior in complex liquids, like cellular interiors, suggests modifications to standard models.
- Diffusing diffusivity is a proposed mechanism for this anomalous behavior.
Purpose of the Study:
- To investigate the impact of diffusing diffusivity on condensed phase reaction dynamics.
- To analyze how multiplicative Ornstein-Uhlenbeck (O-U) noise affects barrier crossing statistics.
- To derive exact expressions for key dynamic measures.
Main Methods:
- A theoretical model simulating a point particle in a double-well potential was developed.
- Thermal fluctuations coupled multiplicatively to Ornstein-Uhlenbeck (O-U) noise were incorporated.
- Barrier crossing statistics, including survival probability and mean first passage time, were calculated.
Main Results:
- Exact expressions for survival probability, mean first passage time, and distribution were derived.
- The O-U relaxation timescale was found to induce dynamic heterogeneity in these quantities.
- The derived expressions differ in appearance from Kramers' formulas but remain consistent.
Conclusions:
- Diffusing diffusivity significantly modifies conventional reaction dynamics models.
- Dynamic heterogeneity is a key consequence of this mechanism in complex systems.
- The study provides a theoretical framework consistent with, yet distinct from, established theories.
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