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Diffusion caused by two noises-active and thermal

Goswami, Koushik and Sebastian, K L (2019) Diffusion caused by two noises-active and thermal. In: JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2019 (8).

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Official URL: https:/dx.doi.org/10.1088/1742-5468/ab2acd


The diffusion of colloids inside an active system-e.g. within a living cell or the dynamics of active particles itself (e.g. self-propelled particles) can be modeled through overdamped Langevin equation which contains an additional noise term apart from the usual white Gaussian noise, originating from the thermal environment. The second noise is referred to as `active noise' as it arises from activity such as chemical reactions. The probability distribution function (PDF or the propagator) in space-time along with moments provides essential information for understanding their dynamical behavior. Here we employ the phase-space path integral method to obtain the propagator, thereby moments and PDF for some possible models for such noise. At first, we discuss the diffusion of a free particle driven by active noise. We consider four different possible models for active noise, to capture the possible traits of such systems. We show that the PDF for systems driven by noises other than Gaussian noise largely deviates from normal distribution at short to intermediate time scales as a manifestation of out-of-equilibrium state, albeit converges to Gaussian distribution after a long time as a consequence of the central limit theorem. We extend our work to the case of a particle trapped in a harmonic potential and show that the system attains steady state at long time limit. Also, at short time scales, the nature of distribution is different for different noises, e.g. for particle driven by dichotomous noise, the probability is mostly concentrated near the boundaries whereas a long exponential tail is observed for a particle driven by Poissonian white noise.

Item Type: Journal Article
Additional Information: copy right of this article belong to IOP PUBLISHING LTD
Keywords: diffusion; noise models; active matter; self propelled particles
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 11 Dec 2019 11:45
Last Modified: 11 Dec 2019 11:45
URI: http://eprints.iisc.ac.in/id/eprint/64074

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