# Characterizing rare fluctuations in soft particulate flows

## TL;DR

This paper investigates the mechanisms of rare fluctuations in soft particulate flows, revealing their different origins relative to the jamming transition, proposing a fluctuation relation, and introducing an effective temperature concept.

## Contribution

It uncovers the origins of rare fluctuations above and below the jamming density and proposes a local fluctuation relation leading to an effective temperature in soft particulate flows.

## Key findings

- Rare fluctuations originate differently depending on the density regime.
- A time-independent local fluctuation relation is verified numerically.
- An effective temperature is introduced and compared with kinetic temperature.

## Abstract

Soft particulate media include a wide range of systems involving athermal dissipative particles both in non-living and biological materials. Characterization of flows of particulate media is of great practical and theoretical importance. A fascinating feature of these systems is the existence of a critical rigidity transition in the dense regime dominated by highly intermittent fluctuations that severely affects the flow properties. Here, we unveil the underlying mechanisms of rare fluctuations in soft particulate flows. We find that rare fluctuations have different origins above and below the critical jamming density and become suppressed near the jamming transition. We then conjecture a time-independent local fluctuation relation, which we verify numerically, and that gives rise to an effective temperature. We discuss similarities and differences between our proposed effective temperature with the conventional kinetic temperature in the system by means of a universal scaling collapse.