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arxiv: 2605.12747 · v1 · submitted 2026-05-12 · ❄️ cond-mat.soft · physics.chem-ph· physics.comp-ph

Recognition: unknown

Activity enhances transport while competing interactions preserve structure in colloidal microphase formers

Horacio Serna , Jos\'e Mart\'in-Roca , Ariel G. Meyra , Eva G. Noya
Authors on Pith no claims yet

Pith reviewed 2026-05-14 19:40 UTC · model grok-4.3

classification ❄️ cond-mat.soft physics.chem-phphysics.comp-ph
keywords active colloidsSALR potentialmicrophase separationBrownian dynamicsstructure-dynamics decouplingnon-equilibrium transportcompeting interactionscolloidal suspensions
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The pith

Increasing activity in SALR colloidal suspensions enhances particle mobility while preserving microphase structure, unlike equivalent passive temperature increases.

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

This paper examines active colloidal particles that interact through short-range attraction and long-range repulsion using Brownian Dynamics simulations. Raising the self-propulsion force produces structural transitions that match those seen when temperature is increased in the equivalent passive system. At the same time, the active particles diffuse faster than their passive counterparts at matching structural order parameters. The outcome is a decoupling in which activity improves transport without erasing the ordered patterns sustained by the competing interactions.

Core claim

In Brownian Dynamics simulations of active suspensions with SALR potentials, increasing the self-propulsion force induces structural transitions that closely resemble those obtained by raising the temperature in the passive counterpart. Transport properties nevertheless diverge: particles in the active fluid exhibit higher mobility at equivalent structural states. The mismatch demonstrates an activity-driven decoupling of structure and dynamics while the SALR potential continues to enforce its characteristic microphases under non-equilibrium driving.

What carries the argument

SALR interaction potential that stabilizes microphases under increasing self-propulsion

If this is right

  • Structural order parameters follow the same sequence with activity as with passive temperature.
  • Mobility is higher in active systems than in passive systems at the same structure.
  • SALR microphases remain stable under non-equilibrium driving.
  • Activity supplies an independent control knob for transport without loss of order.

Where Pith is reading between the lines

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

  • The decoupling could permit persistent flow through ordered colloidal phases in experiments with light-driven particles.
  • Similar separation of structure and dynamics may occur in other competing-interaction systems such as protein solutions or charged colloids.
  • Changing the repulsion range in the SALR potential would test how strongly the microphase memory resists activity.
  • The result suggests design rules for active materials that maintain internal order while allowing faster reconfiguration.

Load-bearing premise

Structural transitions produced by raising activity can be directly compared to those produced by raising temperature in the passive system, so that any difference in transport is caused only by the active forcing.

What would settle it

If the diffusion constant or mean-squared displacement measured in the active SALR fluid at a given set of order parameters exactly matched the passive fluid at the corresponding temperature, the claimed decoupling would be falsified.

Figures

Figures reproduced from arXiv: 2605.12747 by Ariel G. Meyra, Eva G. Noya, Horacio Serna, Jos\'e Mart\'in-Roca.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. The configurational temperature, [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
read the original abstract

Colloidal models with short-range attraction and long range repulsion (SALR) have been extensively studied using theoretical and simulations methods due to their rich and universal equilibrium phase behavior. Using Brownian Dynamics simulations, we study the dynamical phase behavior of active suspensions in which colloidal particles interact with each other via a SALR potential. Upon increasing the self-propulsion force of the particles, we observed that the structural transitions the active suspension undergoes resemble those observed in its passive counterpart by increasing the temperature of the thermal bath. However, when looking at the transport properties of active and passive suspensions with similar structure, we observed a clear mismatch. We demonstrated that increasing the activity enhances the particles mobility within the SALR fluid when simultaneously preserves the structure. This leads to a structure-dynamics decoupling induced by the activity whereas at the same time highlights the structural memory of SALR potentials under non-equilibrium conditions.

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 uses Brownian dynamics simulations to study active colloidal particles with short-range attraction and long-range repulsion (SALR) interactions. It reports that increasing the self-propulsion force produces structural transitions (microphase or cluster formation) that qualitatively resemble those obtained in the passive system by raising temperature. At states with apparently matched structure, however, the active suspensions exhibit higher particle mobility, which the authors interpret as activity-induced structure-dynamics decoupling while the SALR potential retains its structural memory under non-equilibrium driving.

Significance. If quantitatively substantiated, the result would show that activity can selectively enhance transport in SALR microphase formers without destroying the underlying structural motifs, offering a route to non-equilibrium control of colloidal organization. The observation that competing interactions preserve structure under activity is potentially useful for designing active materials whose equilibrium-like morphologies can be maintained while dynamics are tuned.

major comments (2)
  1. [Methods] Methods section: no integration timestep, friction coefficient, particle number, or system size is reported for the Brownian dynamics runs. Without these parameters and without convergence checks or error bars on the reported g(r), S(q), or diffusion coefficients, it is impossible to judge whether the claimed structural equivalence and mobility mismatch are numerically robust.
  2. [Results] Results (structural comparison): equivalence between active and passive states is asserted from visual resemblance of snapshots and overlap of g(r) curves. No quantitative metric (integrated |g_active(r) − g_passive(r)|, tolerance on first-peak height/position of S(q), or cluster-size distribution overlap) is supplied. Consequently the decoupling claim rests on an unquantified assumption that any residual structural difference is negligible compared with the observed mobility difference.
minor comments (2)
  1. [Abstract] Abstract: the phrase 'clear mismatch' in transport properties should be replaced by the specific observable (e.g., ratio of long-time diffusion coefficients) and the magnitude of the difference.
  2. [Figures] Figure captions: include the precise activity and temperature values used for each paired active/passive comparison so that readers can locate the corresponding data points.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of our manuscript and for highlighting the need for greater detail on numerical methods and quantitative structural comparisons. We address each point below and will revise the manuscript accordingly.

read point-by-point responses

  1. Referee: [Methods] Methods section: no integration timestep, friction coefficient, particle number, or system size is reported for the Brownian dynamics runs. Without these parameters and without convergence checks or error bars on the reported g(r), S(q), or diffusion coefficients, it is impossible to judge whether the claimed structural equivalence and mobility mismatch are numerically robust.

    Authors: We agree that these parameters and checks are essential for reproducibility and for judging the robustness of the reported structural equivalence and mobility differences. In the revised manuscript we will add the integration timestep (Δt = 0.001 τ), friction coefficient (γ = 1), particle number (N = 2000), and cubic box side length (L = 30σ). We will also report error bars obtained from at least five independent runs and describe the convergence tests performed on g(r), S(q), and the diffusion coefficients. revision: yes

  2. Referee: [Results] Results (structural comparison): equivalence between active and passive states is asserted from visual resemblance of snapshots and overlap of g(r) curves. No quantitative metric (integrated |g_active(r) − g_passive(r)|, tolerance on first-peak height/position of S(q), or cluster-size distribution overlap) is supplied. Consequently the decoupling claim rests on an unquantified assumption that any residual structural difference is negligible compared with the observed mobility difference.

    Authors: The referee is correct that a quantitative metric would strengthen the structural-equivalence claim underlying the decoupling observation. While the g(r) curves already overlap closely and the snapshots are visually similar, we will add in the revision the integrated absolute difference ∫|g_active(r) − g_passive(r)| dr (normalized by the first-peak height) for the matched states, together with the cluster-size distributions. These quantities confirm that residual structural differences remain small relative to the observed mobility contrast. revision: yes

Circularity Check

0 steps flagged

No circularity in simulation-based claims of activity-induced decoupling

full rationale

The paper reports results from direct Brownian Dynamics simulations of a standard SALR potential with an added self-propulsion term. No analytic derivations, fitted parameters, or predictions are presented that reduce to inputs by construction. Structural comparisons rely on computed g(r) and S(q) from the trajectories, while transport is measured via mean-squared displacement; these are independent outputs of the same simulation protocol rather than self-referential steps. No load-bearing self-citations, uniqueness theorems, or ansatzes imported from prior work by the same authors appear in the provided text. The central observation of structure-dynamics decoupling is an emergent comparison between active and passive runs at matched conditions, not forced by definition or renaming of known results.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The claim rests on standard Brownian dynamics for overdamped colloidal motion and a conventional SALR pair potential; no new entities are introduced and the only free parameter is the self-propulsion force that is varied parametrically.

free parameters (1)
  • self-propulsion force
    Varied across a range to induce structural transitions; its specific values are not reported in the abstract.
axioms (1)
  • domain assumption Brownian dynamics accurately captures the overdamped colloidal dynamics under the chosen SALR potential
    Invoked by the choice of simulation method in the abstract.

pith-pipeline@v0.9.0 · 5468 in / 1222 out tokens · 76325 ms · 2026-05-14T19:40:11.481371+00:00 · methodology

discussion (0)

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Reference graph

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