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Hydrodynamics without Averaging -- a Hard Rods Study

by Friedrich Hübner

Submission summary

Authors (as registered SciPost users): Friedrich Hübner
Submission information
Preprint Link: scipost_202601_00015v1  (pdf)
Date submitted: Jan. 7, 2026, 11:09 p.m.
Submitted by: Friedrich Hübner
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Condensed Matter Physics - Theory
Approaches: Theoretical, Computational

Abstract

On the example of the integrable hard rods model we study the quality of the (generalized) hydrodynamic approximation on a single coarse-grained sample. This is opposed to the traditional approach which averages over an appropriate local equilibrium state. While mathematically more ambiguous, a major advantage of the new approach is that it allows us to disentangle intrinsic diffusion from `diffusion from convection' effects. For the hard rods we find intrinsic diffusion is absent, which agrees with and clarifies recent findings. Interestingly, the results also apply to not locally thermal states, demonstrating that hydrodynamics (in this model) does not require the assumption of local equilibrium.

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

I will attach a pdf letter in a comment (unfortunately, it is not possible to attach a pdf here).

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In refereeing

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Comments

Friedrich Hübner  on 2026-01-07  [id 6208]

Please find the reply letter attached here

Attachment:

reply.pdf