Arrow of time and entropy production in active fluctuations

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• Edgar Roldan (ICTP, Trieste, Italy)
• Tuesday 04 December 2018, 13:00-14:00
• MR11, CMS.

If you have a question about this talk, please contact Professor Mike Cates.

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Active systems are maintained out of equilibrium by processes that consume resources of energy and produce entropy. A well studied example of active cellular fluctuations are spontaneous oscillations of mechanosensory hair bundles of auditory hair cells. Active processes do not obey in general the fluctuation-dissipation theorem: measuring both the linear response of the system to weak external stimuli and spontaneous fluctuations provides a means to quantify deviations from thermal equilibrium. For active fluctuations without drift, such as spontaneous oscillations, it is unclear how entropy production can be characterized.

We introduce lower bounds for the rate of entropy production of an active process by quantifying the degree of time irreversibility of stochastic traces obtained from non-equilibrium mesoscopic degrees of freedom [1]. Our measures of irreversibility reveal signatures of time’s arrow and provide bounds for entropy production even in the case of active fluctuations that have no drift. We apply these irreversibility measures to experimental recordings of ~200 spontaneous hair-bundle oscillations from the ear of the bullfrog Rana Catesbeiana. Our technique allows not only to discriminate between experimental recordings of active and passive hair-bundle oscillations but also to estimate the minimal entropy production required to sustain such oscillations. Notably, our approach can be applied to any physical system where at least one mesoscopic degree of freedom that is even under time reversal can be measured experimentally.

[1] É. Roldán, J. Barral, P. Martin, J.M.R. Parrondo and F. Jülicher arXiv:1801.01574 (2018).

This talk is part of the DAMTP Statistical Physics and Soft Matter Seminar series.

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