Yielding and large deviations in micellar gels: a model

TL;DR

This paper introduces a simple rheological model for micellar gels that captures yield behavior, large deviations, and fluctuation relations, revealing complex fluctuation phenomena near the yielding transition.

Contribution

The model combines kinetics and shear effects to explain experimental rheology and analyzes large deviation functions and fluctuation relations near yield points.

Findings

LDF becomes non-quadratic near the yield threshold

Steady-state fluctuation relation holds at small forces

FR is violated near the transition from flowing to jammed state

Abstract

We present a simple model to account for the rheological behavior observed in recent experiments on micellar gels. The model combines attachment-detachment kinetics with stretching due to shear, and shows well-defined jammed and flowing states. The large deviation function (LDF) for the coarse-grained velocity becomes increasingly non-quadratic as the applied force $F$ is increased, in a range near the yield threshold. The power fluctuations are found to obey a steady-state fluctuation relation (FR) at small $F$. However, the FR is violated when $F$ is near the transition from the flowing to the jammed state although the LDF still exists; the antisymmetric part of the LDF is found to be nonlinear in its argument. Our approach suggests that large fluctuations and motion in a direction opposite to an imposed force are likely to occur in a wider class of systems near yielding.