Volume 117, Number 5, March 2017
|Number of page(s)||7|
|Published online||10 May 2017|
Evaluating linear response in active systems with no perturbing field
Department of Chemistry, Colorado State University - Fort Collins, CO 80523, USA and Laboratoire Charles Coulomb, UMR 5221 CNRS, Université de Montpellier - Montpellier, France
Received: 30 November 2016
Accepted: 9 April 2017
We present a method for the evaluation of time-dependent linear response functions for systems of active particles propelled by a persistent (colored) noise from unperturbed simulations. The method is inspired by the Malliavin weights sampling method proposed by Warren and Allen (Phys. Rev. Lett., 109 (2012) 250601) for out-of-equilibrium systems of passive Brownian particles. We illustrate our method by evaluating two linear response functions for a single active particle in an external harmonic potential. As an application, we calculate the time-dependent mobility function and an effective temperature, defined through the Einstein relation between the self-diffusion and mobility coefficients, for a system of many active particles interacting via a screened Coulomb potential. We find that this effective temperature decreases with increasing persistence time of the self-propulsion. Initially, for not too large persistence times, it changes rather slowly, but then it decreases markedly when the persistence length of the self-propelled motion becomes comparable with the particle size.
PACS: 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion / 05.70.Ln – Nonequilibrium and irreversible thermodynamics / 82.70.Dd – Colloids
© EPLA, 2017
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