Experimental evidence for three universality classes for reaction fronts in disordered flows

TL;DR

This study experimentally identifies three universality classes of reaction front behavior in disordered flows, revealing how mean flow velocity influences roughening, pinning, and depinning transitions in a one-dimensional system.

Contribution

It provides the first experimental evidence for three distinct universality classes in reaction fronts within disordered media, aligning with theoretical predictions.

Findings

Three universality classes observed: KPZ, positive-qKPZ, negative-qKPZ.

Distinct depinning transitions for the quenched KPZ classes.

Front fluctuations controlled by mean flow velocity.

Abstract

Self-sustained reaction fronts in a disordered medium subject to an external flow display self-affine roughening, pinning and depinning transitions. We measure spatial and temporal fluctuations of the front in $1+1$ dimensions, controlled by a single parameter, the mean flow velocity. Three distinct universality classes are observed, consistent with the Kardar-Parisi-Zhang (KPZ) class for fast advancing or receding fronts, the quenched KPZ class (positive-qKPZ) when the mean flow approximately cancels the reaction rate, and the negative-qKPZ class for slowly receding fronts. Both quenched KPZ classes exhibit distinct depinning transitions, in agreement with the theory.