Work to insert a particle into an active fluid

TL;DR

This paper explores the work required to insert a particle into an active fluid, examining how it varies with activity, density, and protocol, revealing protocol dependence and non-Gaussian fluctuations.

Contribution

It introduces a detailed analysis of particle insertion work in active fluids, highlighting its protocol dependence and contrasting it with steady-state density behaviors.

Findings

Average work decreases with activity.

Work fluctuations have asymmetric non-Gaussian tails.

Opposing trends observed between density and insertion work.

Abstract

The chemical potential is defined as the work to quasi-statically add a particle to an equilibrium system. Inspired by this definition, we investigate how the work to add a particle to an active fluid depends on the activity, density, and insertion protocol. We find that the average work is protocol dependent and decreases with activity. Moreover, the work fluctuations retain asymmetric non-Gaussian tails even for slow particle insertions. We then compare the average particle-insertion work to the steady-state densities observed when two active fluids are brought into diffusive contact and observe opposing trends between density and work.