Pith Number

pith:XZT5XZMV

pith:2026:XZT5XZMVOLD2ZVG5MZWBV35R46

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From bulk to interface dynamics, in and out of equilibrium

Fr\'ed\'eric van Wijland, Julien Tailleur, Lila Sarfati

A dynamical-action approach derives linear interface relaxation and fluctuations from bulk hydrodynamics for both equilibrium and non-equilibrium systems.

arxiv:2605.16503 v1 · 2026-05-15 · cond-mat.stat-mech · cond-mat.soft

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Claims

C1strongest claim

Using a well-chosen definition for the interface and the dynamical-action formalism to represent path probabilities, we derive the linear relaxation of the interface and the fluctuations around it for a large class of models. Our method applies to equilibrium dynamics, where it recovers and complements existing results, but also extends to their non-equilibrium counterparts.

C2weakest assumption

The interface remains weakly deformed and the two phases stay stable, so that the fluctuating hydrodynamics plus dynamical-action formalism can be projected onto interface coordinates without uncontrolled approximations.

C3one line summary

Derives interface dynamics and fluctuations from bulk fluctuating hydrodynamics for equilibrium and non-equilibrium models, with a warning on a popular ansatz for active systems.

References

126 extracted · 126 resolved · 5 Pith anchors

[1] (1) with a nonequilibrium drivew[ϕ] = −λ(∇ϕ)2, leading to: ∂tϕ=− δF δϕ −λ(∇ϕ) 2 + √ 2T η(r, z, t),(146) whereF[ϕ] remains given by Eq

[2] (149), withu 0 =ℓ 0

[3] Motivations for introducing active model B+ Let us now turn to the simplest nonequilibrium generalization of model B. In active matter, the motility-induced phase separation [100–106] under- gone by p

[4] (170) The lack of steady-state current enforces the stronger constraint jc =−∂ z −∂2 z mc +f ′(mc) + 2λ−ζ 2 (∂zmc)2 = 0

[5] This breaking of time-reversal symmetry is expected to generate a KPZ nonlin- earity

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Receipt and verification

First computed	2026-05-20T00:02:26.083079Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

be67dbe59572c7acd4dd666c1aefb1e7b063ce36bc536d69b62e5ee2bade21e6

Aliases

arxiv: 2605.16503 · arxiv_version: 2605.16503v1 · doi: 10.48550/arxiv.2605.16503 · pith_short_12: XZT5XZMVOLD2 · pith_short_16: XZT5XZMVOLD2ZVG5 · pith_short_8: XZT5XZMV

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Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/XZT5XZMVOLD2ZVG5MZWBV35R46 \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: be67dbe59572c7acd4dd666c1aefb1e7b063ce36bc536d69b62e5ee2bade21e6

Canonical record JSON

{
  "metadata": {
    "abstract_canon_sha256": "54b9a92dea001f467243106bf8c685aa2ce3f575106d8be6e53cf9a7aae037b9",
    "cross_cats_sorted": [
      "cond-mat.soft"
    ],
    "license": "http://creativecommons.org/licenses/by/4.0/",
    "primary_cat": "cond-mat.stat-mech",
    "submitted_at": "2026-05-15T18:00:53Z",
    "title_canon_sha256": "f5c35a9f19bee1836f18af5954e99c7393976acee2d41b658bd81ee43ac86fbe"
  },
  "schema_version": "1.0",
  "source": {
    "id": "2605.16503",
    "kind": "arxiv",
    "version": 1
  }
}