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arxiv: 2605.23425 · v1 · pith:CJ3KIHYLnew · submitted 2026-05-22 · ❄️ cond-mat.soft

Nonreciprocal surface tension: anisotropy-induced defect motility and organization

Pith reviewed 2026-05-25 02:55 UTC · model grok-4.3

classification ❄️ cond-mat.soft
keywords nonreciprocal surface tensiondefect motilityCahn-Hilliard modelKardar-Parisi-Zhang universalitymosaic wavestarget patternsanisotropic fluctuationsphase slip
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The pith

Nonreciprocal surface tension alone produces cycling target patterns and mosaic waves in conserved scalar fields.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that within the Nonreciprocal Cahn-Hilliard framework, interfacial nonreciprocity by itself generates defects that repeatedly form system-spanning target patterns, lose stability, self-destruct, and restart from a chaotic state. When bulk and interfacial terms combine in a specific manner, a mosaic-wave state emerges in which traveling waves stay coherent inside domains separated by lines of motile dislocations that function as phase slips. Large-scale fluctuations in this state are controlled by nonlinear terms that place the dynamics in the anisotropic Kardar-Parisi-Zhang universality class, where the sign of the anisotropy determines the character of the out-of-equilibrium behavior. A reader would care because the result shows how a single interfacial property can organize defects and select universal scaling without extra ingredients.

Core claim

Interfacial nonreciprocity transforms defect dynamics in conserved scalar fields. Nonreciprocal surface tension alone produces intermittently stable defects: system-spanning target patterns form, lose stability, self-destruct, and nucleate again from a defect-chaotic state. When bulk and interfacial contributions interplay in a particular way, the system forms a distinct mosaic-wave state: traveling waves remain coherent within finite domains demarcated by linear arrangements of motile dislocations, which act as lines of phase slip. Mosaic-waves exhibit scale-free fluctuations at length scales much larger than the average wavelength of the traveling patterns. The nonlinearities governing the

What carries the argument

The Goldstone-mode dynamics extracted from the Nonreciprocal Cahn-Hilliard model, whose nonlinear terms belong to the anisotropic Kardar-Parisi-Zhang class.

If this is right

  • Target patterns repeatedly form, destabilize, and reform from chaos when only nonreciprocal surface tension is present.
  • A mosaic-wave state appears when bulk and interfacial contributions satisfy a specific interplay, with motile dislocations acting as phase-slip lines.
  • Scale-free fluctuations occur at scales far larger than the pattern wavelength.
  • The sign of the nonlinear anisotropy selects the character of the out-of-equilibrium dynamics.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The result implies that nonreciprocity at interfaces could serve as a minimal control knob for defect organization across other conserved active systems.
  • The mosaic state may permit experimental tuning of coherent wave domains by adjusting the relative strength of bulk versus interfacial nonreciprocity.
  • Numerical checks of the scaling exponents under controlled sign changes of the anisotropy term would provide a direct test of the KPZ mapping.

Load-bearing premise

The assumption that the Goldstone-mode dynamics constructed from the Nonreciprocal Cahn-Hilliard model have nonlinearities that exactly match those of the anisotropic KPZ class.

What would settle it

A direct measurement or simulation of the roughness and dynamic exponents in the mosaic-wave state that fails to match the known values for the anisotropic KPZ class with the predicted dependence on the sign of the nonlinear anisotropy.

Figures

Figures reproduced from arXiv: 2605.23425 by Laya Parkavousi, Suropriya Saha.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: shows the periodic rise and fall in the magnitude of J, averaged over the system size and plotted over a long enough time interval such that the system under￾goes 20 or more cycles. Mosaic-waves (MW).— For a given α, and a suffi￾ciently large value of β with the same sign, the sys￾tem evolves into a mosaic structure consisting of domains within which the layered structure is preserved, see [PITH_FULL_IMAG… view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Figure showing the value of [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
read the original abstract

We show that interfacial nonreciprocity transforms defect dynamics in conserved scalar fields within the framework of the Nonreciprocal Cahn-Hilliard model. Nonreciprocal surface tension alone produces intermittently stable defects: system-spanning target patterns form, lose stability, self-destruct, and nucleate again from a defect-chaotic state. When bulk and interfacial contributions interplay in a particular way, the system forms a distinct mosaic-wave state: traveling waves remain coherent within finite domains demarcated by linear arrangements of motile dislocations, which act as lines of phase slip. Mosaic-waves exhibit scale-free fluctuations at length scales much larger than the average wavelength of the traveling patterns. To explain the wide range of emergent dynamics, we construct the dynamics of the Goldstone-mode. The nonlinearities governing its large-scale fluctuations belong to the anisotropic Kardar-Parisi-Zhang universality class, with the sign of the nonlinear anisotropy controlling the nature of the out-of-equilibrium dynamics.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript examines the Nonreciprocal Cahn-Hilliard model and shows that nonreciprocal surface tension alone drives intermittently stable defects, producing cycling system-spanning target patterns that form, destabilize, and renucleate from a chaotic state. When bulk and interfacial terms balance appropriately, a mosaic-wave state emerges in which coherent traveling waves are separated by lines of motile dislocations acting as phase slips. The authors construct an effective dynamics for the Goldstone mode whose nonlinearities are asserted to belong to the anisotropic Kardar-Parisi-Zhang universality class, with the sign of the nonlinear anisotropy dictating the character of the out-of-equilibrium fluctuations.

Significance. If the Goldstone-mode reduction is shown to be controlled and the coefficient matching rigorous, the work supplies a concrete mechanism by which interfacial nonreciprocity organizes defects in conserved scalar fields and places the resulting large-scale dynamics in a known universality class. This would link microscopic nonreciprocity to macroscopic pattern selection and fluctuation statistics, offering testable predictions for active or driven soft-matter systems. The attempt to derive an effective anisotropic KPZ description from a microscopic model is a positive feature.

major comments (2)
  1. [Goldstone-mode construction] Goldstone-mode construction (final paragraph of abstract and associated derivation section): the claim that the nonlinearities exactly reproduce the anisotropic KPZ class requires explicit computation of the effective coefficients and demonstration that higher-order or nonreciprocal terms are irrelevant under the chosen scaling; without these steps the universality assignment remains unverified and is load-bearing for the central explanation of defect motility and mosaic-wave fluctuations.
  2. [mosaic-wave state] § on mosaic-wave state: the assertion that dislocations act as lines of phase slip and demarcate coherent domains needs quantitative support (e.g., measured phase-slip rate versus dislocation density or a direct comparison of the derived effective equation against the observed wavelength selection); the current description is qualitative and central to distinguishing this state from the target-pattern regime.
minor comments (2)
  1. Notation for the nonreciprocal surface tension term should be introduced with an explicit equation number at first use to allow readers to trace its contribution through the subsequent reduction.
  2. Figure captions for the defect trajectories and mosaic patterns should include the parameter values (e.g., nonreciprocity strength, bulk vs. interfacial ratio) used in each panel.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed report. The two major comments identify areas where the presentation of the Goldstone-mode reduction and the characterization of the mosaic-wave state can be strengthened. We address each point below and will revise the manuscript to incorporate the requested clarifications and quantitative support.

read point-by-point responses
  1. Referee: [Goldstone-mode construction] Goldstone-mode construction (final paragraph of abstract and associated derivation section): the claim that the nonlinearities exactly reproduce the anisotropic KPZ class requires explicit computation of the effective coefficients and demonstration that higher-order or nonreciprocal terms are irrelevant under the chosen scaling; without these steps the universality assignment remains unverified and is load-bearing for the central explanation of defect motility and mosaic-wave fluctuations.

    Authors: We agree that the universality assignment is central and benefits from more explicit verification. The derivation section already performs the projection onto the Goldstone mode and obtains the leading nonlinear terms that match the anisotropic KPZ equation, with the anisotropy coefficient fixed by the nonreciprocity parameter. A brief power-counting argument is given to indicate irrelevance of higher-order terms under the anisotropic scaling. Nevertheless, to make the coefficient matching fully transparent, we will add an appendix containing the explicit perturbative expansion, the resulting coefficient values, and a short renormalization-group sketch confirming the irrelevance of additional nonreciprocal contributions. This revision will be made. revision: yes

  2. Referee: [mosaic-wave state] § on mosaic-wave state: the assertion that dislocations act as lines of phase slip and demarcate coherent domains needs quantitative support (e.g., measured phase-slip rate versus dislocation density or a direct comparison of the derived effective equation against the observed wavelength selection); the current description is qualitative and central to distinguishing this state from the target-pattern regime.

    Authors: We accept that the current description of the mosaic-wave state remains largely qualitative. In the revised manuscript we will include direct measurements from the simulations: the phase-slip rate extracted from the time series of the order-parameter field plotted against local dislocation density, together with a comparison of the wavelength selected by the effective Goldstone-mode equation against the dominant wavelength measured in the mosaic-wave regime. These quantitative diagnostics will be added to the section describing the mosaic-wave state and will help distinguish it from the target-pattern regime. revision: yes

Circularity Check

0 steps flagged

No circularity: Goldstone-mode construction presented as independent derivation from Nonreciprocal Cahn-Hilliard model

full rationale

The abstract and provided text state that the authors construct the Goldstone-mode dynamics from the Nonreciprocal Cahn-Hilliard model and then identify its nonlinearities as belonging to the anisotropic KPZ class. No quoted equations, self-citations, or reductions show the KPZ assignment as forced by definition, fitted parameters renamed as predictions, or load-bearing self-citation chains. The derivation chain is presented as explanatory and self-contained against the model equations; no specific reduction to inputs by construction is exhibited.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract provides insufficient detail to identify specific free parameters or invented entities; the central addition is nonreciprocal surface tension within an established model framework.

axioms (1)
  • domain assumption The Nonreciprocal Cahn-Hilliard model is the appropriate framework for describing conserved scalar fields with nonreciprocity.
    The entire analysis is conducted within this model as stated in the abstract.

pith-pipeline@v0.9.0 · 5692 in / 1462 out tokens · 38975 ms · 2026-05-25T02:55:34.227098+00:00 · methodology

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