{"id":"ff664f0a-9099-4ac8-9c77-c6f5222f5621","arxiv_id":"2603.18909","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":5,"one_line_summary":"In the α-ROM at criticality, avalanche size, duration and participation are power-law distributed, and the avalanche fractal dimension crosses d≈2 near α≈1.5, switching compact to sparse geometry.","lead":"Simulations of a particle model for sheared suspensions show that near the reversible-irreversible transition, activity comes in power-law avalanches whose geometry flips from compact to sparse as fluid-mediated interactions get longer-ranged. That geometric crossover is a concrete, measurable signature of how hydrodynamics reshape nonequilibrium criticality.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified beyond the reader's already-flagged criticality/reactivation assumptions.","rationale":"The paper's strongest claim is a clean geometric statement about avalanche fractal dimension crossing space dimension as interaction range is tuned. All supporting evidence presented (power-law collapses, compensated plots, conditional averages, space-time activity maps, and the depinning scaling relation) is mutually consistent and uses standard methods for absorbing-state / depinning models. The only soft spots that actually underwrite the claim are precisely those already named by the reader: exact criticality inherited from [25] and an untested reactivation protocol. Because those concerns are already reflected in the CONDITIONAL verdict and the HIGH-but-not-definitive confidence, no further adjustment is warranted. Code/data release and error bars would raise the grade but are not required to keep the present conditional acceptance.","tokens_in":14127,"tokens_out":609,"duration_ms":6995,"concrete_test":"Re-run the finite-size collapses of P(S) and ⟨N⟩S for α=1.5 and α=1.25 at three packing fractions ϕ=ϕc(α)±δ with δ of order the uncertainty quoted in [25]; if the best-collapse df moves by more than ~0.1 or the df>d vs df<d assignment reverses, the geometric crossover claim is protocol/criticality-sensitive and should be downgraded.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central geometric claim (df crossing d=2 near α*≈1.5, with compact vs sparse avalanches) is internally consistent with the multi-size collapses of P(S), P(T), P(N) (Figs. 1–3, 10–12), the conditional averages (Fig. 6), the space-time plots (Fig. 5), and the successful depinning scaling check β=ν⊥(d-df+z) (Fig. 7). The reader's weakest assumption correctly isolates the two places where the claim is least secure: (i) ϕ is fixed exactly at the α-dependent ϕc taken from the prior static study [25], and (ii) only a single-particle random-reactivation protocol is used, with no protocol-variation test of whether df, z, χ themselves shift. No stronger, independent load-bearing flaw (e.g., an internal inconsistency in the scaling forms, a misdefinition of S or N, or a contradiction with the reported cluster exponents) is visible in the manuscript.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript studies intermittent avalanche dynamics at the reversible–irreversible (absorbing) transition of a two-dimensional Random Organization Model with fluid-mediated long-range interactions (α-ROM). Activity is coarse-grained onto a grid and passive particles receive additive Gaussian kicks whose variance is set by a power-law propagator G(r)∼(1+r²)^−α. At the α-dependent critical packing fraction ϕc, avalanches are generated by repeated single-particle random reactivation. Finite-size collapses of P(S), P(T) and P(N) for L=256–2048 yield α-dependent power-law and cutoff exponents (Table I, Figs. 1–4, 10–12). The central geometric claim is that the avalanche fractal dimension df crosses the spatial dimension d=2 near α*≈1.5, so that avalanches are compact (df>d) for short-range interactions and non-compact/sparse (df<d) for long-range ones (Fig. 5). Conditional averages, a depinning-style scaling check β=ν⊥(d−df+z), and power-law cluster statistics inside avalanches are also reported.","tokens_in":14370,"tokens_out":1456,"duration_ms":22255,"significance":"If the reported α-dependence of the avalanche exponents and the compact-to-sparse crossover at α*≈1.5 hold, the work supplies a concrete dynamical probe of interaction-range effects at absorbing transitions that goes beyond the static exponents of the authors’ prior study. The multi-size finite-size collapses, compensated plots, space-time visualizations, and successful check of the large-avalanche scaling relation are genuine strengths and make the geometric claim falsifiable. The α-ROM is a minimal, tunable setting that links the reversible–irreversible transition in sheared suspensions to long-range depinning and conserved directed percolation, and it opens a clear route to experimental comparison (Brownian or sedimentation reactivation). The sequential use of ϕc(α) and static exponents from the companion paper is ordinary and does not undermine novelty of the avalanche analysis.","major_comments":[{"comment":"§III.B: All avalanche distributions are measured after fixing ϕ exactly at the α-dependent critical values ϕc(α) taken from the authors’ static study [25], with no independent re-determination or off-criticality scan in the present work. Because the cutoff exponents df, z, χ (and therefore the claimed crossing df=d near α*≈1.5) are extracted from finite-size collapses that assume criticality, even a small systematic offset in ϕc could bias the reported geometry. A short sensitivity check (e.g., distributions at ϕc±δϕ for one or two α) or an explicit statement of the uncertainty on ϕc would make the central claim more secure.","section":"§III.B"},{"comment":"§III.B and §III.E: Avalanches are generated exclusively by a single-particle random-reactivation protocol. The text correctly notes (citing yielding work [36]) that absolute values of df and z can depend on the reactivation rule while scaling relations may be preserved, yet no second protocol is tested. Given that the geometric distinction compact vs sparse rests on the absolute value of df relative to d=2, at least a brief comparison (or a stronger argument why the single-particle rule is representative of the experimental reactivation mechanisms mentioned) is needed before the α* crossover can be regarded as protocol-independent.","section":"§III.B, §III.E"},{"comment":"§III.E, Eq. (6) and Fig. 7: The test of the depinning scaling relation uses ν⊥ estimated from the hyperscaling formula ν⊥=d−1(2β+γ′) with static exponents taken from [25]. For long-range interactions (especially α≲1.5, where the authors themselves report departure from LR-CDP), hyperscaling is not guaranteed. The main geometric claim does not rely on this test, but the claim that “Eq. (6) is very well followed” should be qualified by an explicit discussion of possible hyperscaling violation, or by an independent estimate of ν⊥.","section":"§III.E, Eq. (6), Fig. 7"}],"minor_comments":[{"comment":"Table I and Fig. 4: No uncertainties are quoted on the fitted exponents. Even rough error bars from the quality of the collapses (or from jackknife over system sizes) would help the reader judge how sharply df crosses d=2.","section":"Table I, Fig. 4"},{"comment":"§II.B, Eq. (3): The piecewise choice of the prefactor c (constant for α>1, L-dependent for α<1) is stated but not motivated beyond numerical convenience; a one-sentence physical or normalization argument would help.","section":"§II.B, Eq. (3)"},{"comment":"§III.F: The cluster graph connectivity threshold √3·2 is introduced without discussion of robustness. A brief remark that the power-law exponents are stable under modest changes of the threshold would strengthen the cluster section.","section":"§III.F"},{"comment":"Figs. 1–3 and 10–12: Compensated plots are useful; adding the fitted exponent value directly on each panel (as done for clusters in Fig. 8) would improve readability.","section":"Figs. 1–3, 10–12"},{"comment":"Abstract and Introduction: “kin depinning” appears to be a typographical remnant of “akin to depinning”; please correct.","section":"Abstract, Introduction"},{"comment":"§I: A short pointer to the experimental reactivation mechanisms (Brownian motion, sedimentation) already appears in §III.B; moving a sentence of that discussion into the introduction would better motivate the avalanche focus for a soft-matter audience.","section":"§I"}],"recommendation":"minor_revision","confidential_remarks":"The manuscript is a natural and well-executed sequel to the authors’ static study of the same model [25]. The avalanche analysis is new and the geometric crossover is interesting. The two load-bearing caveats (exact criticality and single reactivation protocol) are standard in the absorbing-state/avalanche literature and can be addressed by modest additional checks or clearer caveats; they do not warrant rejection. Fit for a solid soft-matter / statistical-physics journal is good."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The one thing worth knowing is that this is the first systematic avalanche study of the mediated Random Organization Model. They measure size, duration and participation distributions at criticality for a range of interaction exponents α, extract the usual power-law and cutoff exponents, and show that the avalanche fractal dimension df crosses the spatial dimension d=2 near α*≈1.5. That produces a clean geometric distinction: compact avalanches for short-range interactions, sparse ones for long-range. That is new relative to the earlier ROM literature and to their own static α-ROM paper.\n\nWhat they do well is standard but careful finite-size work. Collapses of P(S), P(T) and P(N) for L up to 2048 look decent; compensated plots and space-time snapshots make the compact/sparse crossover visible; conditional averages ⟨T⟩S and ⟨N⟩S collapse with the same cutoffs; and the depinning-style relation β=ν⊥(d-df+z) holds when they plug in the static exponents from their previous study. Cluster statistics are a useful extra. The citation pattern is appropriate and the model definition is clear.\n\nSoft spots are real but proportional. Critical packing fractions φc(α) and the static exponents are taken from the earlier paper without a re-determination here, and they use only one reactivation protocol (single random particle). They note that scaling relations may be protocol-independent, but they do not test whether df, z or χ themselves shift. Exponents come from visual collapse with no error bars, and code/data are not released. None of that breaks the central claim; it just means the numbers should be treated as good estimates rather than definitive.\n\nThis is for people working on absorbing transitions, depinning, or sheared suspensions who care about interaction-range effects. It is not paradigm-shifting, but it is the natural next measurement and it is done competently. I would send it to peer review; a serious referee can ask for error bars, a protocol check, and data release without the paper needing to be reinvented. Worth engaging if you work in the area.","headline":"Solid computational paper that finally gives avalanche statistics for the α-ROM and shows df crossing d near α≈1.5; the geometric claim is well supported by the collapses, with only the usual caveats about inherited φc and single reactivation protocol.","tokens_in":15071,"tokens_out":600,"would_cite":true,"duration_ms":5379,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"At the reversible-irreversible transition, long-range fluid interactions turn avalanches from compact to sparse as their fractal dimension crosses space dimension.","keywords":["absorbing phase transition","reversible-irreversible transition","Random Organization Model","avalanches","long-range interactions","fractal dimension","conserved directed percolation","sheared suspensions"],"falsifier":"Measure the fractal dimension of activity bursts in a two-dimensional oscillatory suspension while systematically changing the effective interaction range (for example by changing solvent viscosity or particle size); if df never crosses 2, or if the power-law exponents stay independent of range, the central claim fails.","tokens_in":14950,"feed_emoji":"🌊","tokens_out":695,"duration_ms":6440,"temperature":0.7,"pith_summary":"Cyclically sheared suspensions sit at an absorbing phase transition: below a critical strain they eventually settle into reversible motion; above it they keep colliding forever. Earlier work tracked only global activity or waiting times. This paper instead measures the intermittent bursts of activity at criticality in a Random Organization Model that includes long-range hydrodynamic kicks decaying as a tunable power of distance. The bursts are scale-free avalanches whose size, duration and number of particles obey power laws whose exponents depend continuously on the interaction range. The decisive geometric fact is that the fractal dimension of an avalanche crosses the spatial dimension near a characteristic range: short-range kicks produce compact avalanches that re-activate the same particles many times, while long-range kicks produce sparse, non-compact avalanches. That geometric switch also organises the non-monotonic drift of the power-law exponents and the internal cluster statistics. The result supplies a concrete dynamical probe that experiments on oscillatory suspensions can use to read out the effective range of fluid-mediated interactions.","feed_headline":"Long-range fluid kicks turn avalanches from compact to sparse","feed_subtitle":"Avalanche fractal dimension crosses space dimension near a critical interaction range","key_machinery":"The α-ROM: a stroboscopic particle model in which active (overlapping) particles receive random kicks and also induce random displacements of distant passive particles through a coarse-grained power-law kernel G(r)∼r^{-2α}. Avalanches are defined as temporally connected bursts of activity between successive absorbing states, reactivated by single-particle random kicks.","core_discovery":"At the absorbing critical point of the mediated Random Organization Model, avalanche size, duration and participation number are power-law distributed with exponents that vary continuously with the interaction-decay exponent α. The avalanche fractal dimension df crosses the spatial dimension d=2 near α*≈1.5, so avalanches are compact (df>d) for short-range interactions and non-compact (df<d) for long-range interactions; the same crossover organises the non-monotonic behaviour of the power-law exponents and the cluster statistics inside avalanches.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Long-range fluid mediation sparsifies critical avalanches in ROM","Avalanche fractal dim crosses space dim as interaction range grows","Power-law avalanches switch compact to sparse with longer α","α tunes ROM avalanches from compact (df>d) to sparse (df<d)","Fluid kicks flip avalanche structure across α≈1.5 at criticality"],"cache_read_input_tokens":128,"weakest_assumption_plain":"The packing fraction is set exactly at the previously measured critical density for each interaction range, and the single-particle reactivation protocol used to keep the system alive does not change the reported avalanche cutoff exponents.","fun_headline_variants_meta":{"raw":{"variants":["Long-range fluid mediation sparsifies critical avalanches in ROM","Avalanche fractal dim crosses space dim as interaction range grows","Power-law avalanches switch compact to sparse with longer α","α tunes ROM avalanches from compact (df>d) to sparse (df<d)","Fluid kicks flip avalanche structure across α≈1.5 at criticality"]},"model":"grok-4.5","effort":"low","cost_usd":0.005674,"raw_usage":{"total_tokens":1559,"prompt_tokens":824,"num_sources_used":0,"completion_tokens":77,"cost_in_usd_ticks":56740000,"prompt_tokens_details":{"text_tokens":824,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":658,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":824,"tokens_out":77,"duration_ms":7272,"temperature":1.0,"reasoning_tokens":658,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-13T22:18:50.730811+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Measure the fractal dimension of activity bursts in a two-dimensional oscillatory suspension while systematically changing the effective interaction range (for example by changing solvent viscosity or particle size); if df never crosses 2, or if the power-law exponents stay independent of range, the central claim fails.","supporting_citations":[],"review_version":1}