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Out-of-equilibrium dynamics of two interacting optically-trapped particles
by Victor S Dotsenko, Alberto Imparato, Pascal Viot, Gleb Oshanin
This Submission thread is now published as
Submission summary
| Authors (as registered SciPost users): | Pascal Viot |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2302.07716v1 (pdf) |
| Date accepted: | 2023-05-30 |
| Date submitted: | 2023-02-16 08:46 |
| Submitted by: | Viot, Pascal |
| Submitted to: | SciPost Physics Core |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
We present a theoretical analysis of a non-equilibrium dynamics in a model system consisting of two particles which move randomly on a plane. The two particles interact via a harmonic potential, experience their own (independent from each other) noises characterized by two different temperatures $T_1$ and $T_2$, and each particle is being held by its own optical tweezer. Such a system with two particle coupled by hydrodynamic interactions was previously realised experimentally in B\'erut et al. [EPL {\bf 107}, 60004 (2014)], and the difference between two temperatures has been achieved by exerting an additional noise on either of the tweezers. Framing the dynamics in terms of two coupled over-damped Langevin equations, we show that the system reaches a non-equilibrium steady-state with non-zero (for $T_1 \neq T_2$) probability currents that possess non-zero curls. As a consequence, in this system the particles are continuously spinning around their centers of mass in a completely synchronised way - the curls of currents at the instantaneous positions of two particles have the same magnitude and sign. Moreover, we demonstrate that the components of currents of two particles are strongly correlated and undergo a rotational motion along closed elliptic orbits.
Published as SciPost Phys. Core 6, 056 (2023)
Reports on this Submission
Report #1 by Anonymous (Referee 1) on 2023-5-9 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2302.07716v1, delivered 2023-05-09, doi: 10.21468/SciPost.Report.7173
Strengths
- Clearly defined problem and solid solution
- Of experimental relevance
- Well-written and pedagogical
- Appears to be sound and correct
Weaknesses
- Extends earlier work, rather than being completely original and novel.
Report
The authors investigate theoretically the non-equilibrium dynamics of two interacting particles that move randomly in a plane under the influence of different temperatures. Such a setup has recently been realized experimentally using optical tweezers with effective temperatures implemented by additional noise. The authors find that the particles spin around their centers-of-mass in a synchronised way. Compared to earlier works that focused on a one-dimensional setup, the authors now consider a plane and unravel the dynamical behavior that can occur in two dimensions.
I like the paper and believe that it can be published as it is. The problem is clearly laid out, and the solution seems correct and sound. The findings may also be of relevance to current experimental actitivies.
I just have a few minor comments for the authors to consider:
- I wonder if one can interpret the normalization factor in Eqs. (10,24), with the suggestive letter Z, as a non-equilibrium partition function? If so, would it be possible to extract further information from this quantity, for example, by going beyond average values and consider fluctuations as well?
- The authors might want to proof-read the manuscript one last time; e.g. in the caption of Fig. 4, there is a typo in "averaged".