Non-conservative forces and effective temperatures in active polymers

TL;DR

This paper investigates the dynamics of active polymers with self-propulsion, demonstrating how an effective temperature can be defined and related to motor activity, structure, and tracer diffusion, providing insights into non-equilibrium behavior.

Contribution

It introduces a method to define and analyze an effective temperature in active polymer systems, linking it to motor activity and tracer diffusion, and offers a framework to interpret experimental data.

Findings

Effective temperature exceeds bath temperature with increased motor activity.

Effective temperature correlates with the square of normalized motor strength.

Linear relation between effective temperature and tracer diffusion times density.

Abstract

We follow the dynamics of an ensemble of interacting self-propelled semi-flexible polymers in contact with a thermal bath. We characterize structure and dynamics of the passive system and as a function of the motor activity. We find that the fluctuation-dissipation relation allows for the definition of an effective temperature that is compatible with the results obtained by using a tracer particle as a thermometer. The effective temperature takes a higher value than the temperature of the bath when the effect of the motors is not correlated with the structural rearrangements they induce. Our data are compatible with a dependence upon the square of the motor strength (normalized by the average internal force) and they suggest an intriguing linear dependence on the tracer diffusion constant times the density of the embedding matrix. We show how to use this concept to rationalize experimental results and suggest possible innovative research directions.