Title:	Dynamical fluctuations of a tracer coupled to active and passive particles
Authors:	Santra, Ion
Keywords:	dynamical fluctuations tracer coupled active particles passive particles
Issue Date:	8-Mar-2023
Publisher:	IOP Publishing Ltd.
Citation:	Journal of Physics : Complexity, 2023, Vol. 4,p015013
Abstract:	We study the induced dynamics of an inertial tracer particle elastically coupled to passive or active Brownian particles. We integrate out the environment degrees of freedom to obtain the exact effective equation of the tracer—a generalized Langevin equation in both cases. In particular, we find the exact form of the dissipation kernel and effective noise experienced by the tracer and compare it with the phenomenological modeling of active baths used in previous studies. We show that the second fluctuation-dissipation relation (FDR) does not hold at early times for both cases. However, at finite times, the tracer dynamics violate (obeys) the FDR for the active (passive) environment. We calculate the linear response formulas in this regime for both cases and show that the passive medium satisfies an equilibrium fluctuation response relation, while the active medium does not—we quantify the extent of this violation explicitly. We show that though the active medium generally renders a nonequilibrium description of the tracer, an effective equilibrium picture emerges asymptotically in the small activity limit of the medium. We also calculate the mean squared velocity and mean squared displacement of the tracer and report how they vary with time.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/8064
ISSN:	2632-072X
Alternative Location:	https://arxiv.org/abs/2210.05139 https://doi.org/10.1088/2632-072X/acbf1a https://ui.adsabs.harvard.edu/abs/2022arXiv221005139S/abstract
Copyright:	2023 The Author(s)
Appears in Collections:	Research Papers (TP)

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