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Boundary layers, transport and universal distribution in boundary driven active systems
by Pritha Dolai, Arghya Das
Submission summary
| Authors (as registered SciPost users): | Arghya Das · Pritha Dolai |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202506_00052v2 (pdf) |
| Date accepted: | Sept. 8, 2025 |
| Date submitted: | Aug. 26, 2025, 10:08 a.m. |
| Submitted by: | Arghya Das |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
We discuss analytical results for a run-and-tumble particle (RTP) in one dimension in presence of boundary reservoirs. It exhibits 'kinetic boundary layers', nonmonotonous distribution, current without density gradient, diffusion facilitated current reversal and optimisation on tuning dynamical parameters, and a new transport effect in the steady state. The spatial and internal degrees of freedom together possess a symmetry, using which we find the eigenspectrum for large systems. The eigenvalues are arranged in two bands which can mix in certain conditions resulting in a crossover in the relaxation. The late time distribution for large systems is obtained analytically; it retains a strong and often dominant 'active' contribution in the bulk rendering an effective passive-like description inadequate. A nontrivial 'Milne length' also emerges in the dynamics. Finally, a novel universality is proposed in the absorbing boundary problem for dynamics with short-ranged colored noise. Active processes driven by active reservoirs may thus provide a common physical ground for diverse and new nonequilibrium phenomena.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
We have incorporated the suggested changes in the manuscript based on the latest comments by the referees and your email dated August 25, 2025. Specifically, we have now commented about the dimensions and units at the end of Section 2 (''Model''), and clarified some parts of the Appendix A (''Comments on the boundary magnetisation control''). We have also revised the Acknowledgement.
Our responses to the the comments of the referees are uploaded, and we hereby submit the revised manuscript. We hope this is now suitable for acceptance and publication.
We thank you and the editorial team for your kind assistance in the process. We thank the referees for their time and feedback.
With regards,
Pritha Dolai, Arghya Das
List of changes
- At the end of section 2 (Model: boundary driven RTPs), couple of sentences clarifying the dimensions and units are added: "Note that all the variables... diffusivity in $\mu {\rm m}^2$/s."
- In the caption of Fig. 3, the sentence inside the parenthesis is now started as, "Note that...".
- In the section 4.2, the paragraph headers "spectrum for $o_x = 1$ (even sector)" and "spectrum for $o_x = −1$ (odd sector)" are removed and it is a continuous text now.
- The "Acknowledgements" section is modified and acknowledgement to the reviewers is added.
- Appendix A (Comments on the boundary magnetisation control) is now revised for better clarity.
Published as SciPost Phys. 19, 088 (2025)