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Fluctuation-dissipation in active matter

Burkholder, Eric W. and Brady, John F. (2019) Fluctuation-dissipation in active matter. Journal of Chemical Physics, 150 (18). Art. No. 184901. ISSN 0021-9606. https://resolver.caltech.edu/CaltechAUTHORS:20190520-073652187

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Abstract

In a colloidal suspension at equilibrium, the diffusive motion of a tracer particle due to random thermal fluctuations from the solvent is related to the particle’s response to an applied external force, provided this force is weak compared to the thermal restoring forces in the solvent. This is known as the fluctuation-dissipation theorem (FDT) and is expressed via the Stokes-Einstein-Sutherland (SES) relation D = k_BT/ζ, where D is the particle’s self-diffusivity (fluctuation), ζ is the drag on the particle (dissipation), and k_BT is the thermal Boltzmann energy. Active suspensions are widely studied precisely because they are far from equilibrium—they can generate significant nonthermal internal stresses, which can break the detailed balance and time-reversal symmetry—and thus cannot be assumed to obey the FDT a priori. We derive a general relationship between diffusivity and mobility in generic colloidal suspensions (not restricted to near equilibrium) using generalized Taylor dispersion theory and derive specific conditions on particle motion required for the FDT to hold. Even in the simplest system of active Brownian particles (ABPs), these conditions may not be satisfied. Nevertheless, it is still possible to quantify deviations from the FDT and express them in terms of an effective SES relation that accounts for the ABPs conversion of chemical into kinetic energy.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1063/1.5081725DOIArticle
ORCID:
AuthorORCID
Burkholder, Eric W.0000-0001-7420-4290
Brady, John F.0000-0001-5817-9128
Additional Information:© 2019 Published under license by AIP Publishing. Submitted: 15 November 2018; Accepted: 21 April 2019; Published Online: 9 May 2019. This work was supported in part by the NSF under Grant No. CBET 1437570.
Funders:
Funding AgencyGrant Number
NSFCBET-1437570
Issue or Number:18
Record Number:CaltechAUTHORS:20190520-073652187
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190520-073652187
Official Citation:Fluctuation-dissipation in active matter. Eric W. Burkholder and John F. Brady. The Journal of Chemical Physics 2019 150:18; doi: 10.1063/1.5081725
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95582
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 May 2019 15:00
Last Modified:02 Jun 2020 16:21

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