Experimental Evidence for Three Universality Classes for Reaction Fronts in Disordered Flows

Area of Science:

• Complex systems
• Statistical physics
• Nonlinear dynamics

Background:

• Self-sustained reaction fronts in disordered media are crucial in various physical and chemical processes.
• External flow significantly influences front dynamics, leading to phenomena like pinning and depinning.
• Understanding these dynamics is key to controlling reaction propagation in heterogeneous environments.

Purpose of the Study:

• To investigate the roughening, pinning, and depinning transitions of self-sustained reaction fronts under external flow.
• To identify the universality classes governing front dynamics in a 1+1 dimensional disordered medium.
• To analyze the impact of mean flow velocity on front fluctuations and depinning behavior.

Main Methods:

• Experimental measurement of spatial and temporal fluctuations of reaction fronts.
• System controlled by a single parameter: mean flow velocity.
• Analysis of data to identify distinct universality classes and depinning transitions.

Main Results:

• Observed self-affine roughening, pinning, and depinning transitions.
• Identified three distinct universality classes: Kardar-Parisi-Zhang (KPZ), positive-quenched KPZ (positive-qKPZ), and negative-qKPZ.
• Demonstrated that both qKPZ classes exhibit unique depinning transitions, consistent with theoretical predictions.

Conclusions:

• The dynamics of reaction fronts in disordered media with flow are complex and can be classified into distinct universality classes.
• The mean flow velocity is a critical parameter controlling front behavior and transitions.
• The findings support theoretical models of quenched KPZ dynamics and depinning transitions in such systems.