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SUMMARY:Lévy flights enhance tracer diffusion in active suspensions - Adr
 ian Baule (Queen Mary University of London)
DTSTART:20220321T113000Z
DTEND:20220321T120000Z
UID:TALK171701@talks.cam.ac.uk
DESCRIPTION:The diffusion&nbsp\;process followed by a passive tracer in pr
 ototypical active media such as&nbsp\;suspensions of active colloids or sw
 imming&nbsp\;microorganisms differs&nbsp\;significantly from Brownian moti
 on\, manifest in a greatly enhanced diffusion&nbsp\;coefficient\, non-Gaus
 sian tails of&nbsp\;the&nbsp\;displacement statistics\, and crossover&nbsp
 \;phenomena from non-Gaussian to Gaussian scaling. While such characterist
 ic&nbsp\;features have been&nbsp\;extensively observed in experiments\, th
 ere is so far no&nbsp\;comprehensive theory explaining how they emerge fro
 m the microscopic active&nbsp\;dynamics.&nbsp\;Here we present a theoretic
 al framework of the enhanced tracer diffusion&nbsp\;in an active medium fr
 om its microscopic dynamics by&nbsp\;coarse-graining&nbsp\;the&nbsp\;hydro
 dynamic interactions between the tracer and the active particles as a&nbsp
 \;stochastic process. The tracer is shown to&nbsp\;follow a non-Markovian&
 nbsp\;coloured&nbsp\;Poisson process that accounts quantitatively for all 
 empirical observations [1].&nbsp\;The theory predicts in particular a&nbsp
 \;long-lived L&eacute\;vy flight&nbsp\;regime of the tracer&nbsp\;motion w
 ith a non-monotonic crossover between two different power-law&nbsp\;expone
 nts. Our framework provides the first validation of the celebrated&nbsp\;L
 &eacute\;vy flight&nbsp\;model from a physical&nbsp\;microscopic dynamics.
 &nbsp\;With K. Kanazawa (University of Tsukuba)\, T. Sano (Keio University
 )\, and A. Cairoli (Crick Institute).[1] K. Kanazawa\, T. Sano\, A. Cairol
 i\, A. Baule\;&nbsp\;Nature 579\, 364 (2020)&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
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