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Macroscopic Fluctuation Theory and Current Fluctuations in Active Lattice Gases

by Tal Agranov, Sunghan Ro, Yariv Kafri and Vivien Lecomte

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Submission summary

Authors (as registered SciPost users): Tal Agranov
Submission information
Preprint Link: scipost_202208_00013v2  (pdf)
Date accepted: 2022-12-01
Date submitted: 2022-11-07 15:19
Submitted by: Agranov, Tal
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Statistical and Soft Matter Physics
Approach: Theoretical


We study the current large deviations for a lattice model of interacting active particles displaying a motility-induced phase separation (MIPS). To do this, we first derive the exact fluctuating hydrodynamics of the model in the large system limit. On top of the usual Gaussian noise terms the theory also presents Poissonian noise terms, that we fully account for. We find a dynamical phase transition between flat density profiles and sharply phase-separated traveling waves, and we derive the associated phase diagram together with the large deviation function for all phases, including the one displaying MIPS. We show how the results can be obtained using methods similar to those of equilibrium phase separation, in spite of the nonequilibrium nature of the problem.

List of changes

Dear Editor,
We wish to thank both referees for carefully studying the manuscript, for their positive feedback, and for the very useful comments and suggestions that we have fully implemented. Here is the list of changes made in the manuscript following the referee's comments. We hope that with these changes the manuscript can now be accepted for publication:
1) Referee (II) pointed out the confusing use of the word bias. We fully agree with him. Accordingly, we have modified the text just below equation (28) and avoided the use of "bias".
2) Referee (I) pointed out that the paper "could be made a bit more accessible to a wider audience, not necessarily familiar with MIPS". This was elaborated in his comments No (1), (2), and (3). We found these comments very useful and they helped us revise the text to address the accessibility issue: A) We have slightly reformulated the presentation of the dynamics of the model at the beginning of Sec. II and added a short explanation in the caption of Fig. 1. B) We have added a more detailed derivation and explanation of the fluctuating hydrodynamics. This additional text appears now between Eq. (1) and Eq. (7). C) We have added a detailed explanation for the MIPS and the phase diagram below Eq.(7). we also added a short explanation in the caption of Fig. (2).
3) Following Referee (I) comment No (4) we have changed the symbol \mathbbC -> \mathbfC.
4) Following his comment No (10) we have added a short explanation below Eq.(34) which now better links the text to Fig 5 (B).
5) All of the other typos and grammatical errors were fully implemented.

Published as SciPost Phys. 14, 045 (2023)

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