{"id":"0cf4cf26-afe5-498b-9ded-921e7f86b115","arxiv_id":"2606.10474","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Finite-rate orientational relaxation in a Vicsek-like model drives transitions from isotropic to polar bands, cross-sea, homogeneous polar, and micro-clustered states as alignment rate increases.","lead":"The paper introduces a Langevin model for active particles where orientations relax at finite rate toward the local mean direction, combining Vicsek alignment with XY-like dynamics. Simulations show this relaxation rate acts as a control parameter driving transitions through multiple collective phases.","discovery_kind":"unclear","skeptic_critique":{"model":"grok-4.3","headline":"Finite-size effects and lack of scaling analysis may artifactually produce the reported sequence of phases","rationale":"The reader's weakest assumption directly identifies the numerical robustness issue; the full-text description of the simulation protocol does not add independent evidence (no machine-checked proofs or parameter-free analytics) that would remove this concern, so the UNVERDICTED verdict is unchanged.","tokens_in":1723,"tokens_out":339,"duration_ms":9190,"concrete_test":"Re-run the phase diagram scan at two additional linear sizes (e.g., L=512 and L=1024 if original L\neg1000) with identical parameters; if the locations of the isotropic-band and band-cross-sea transitions shift by more than the reported bin width in alignment rate J, or if the Binder cumulant signatures disappear, the claimed qualitative restructuring is not robust.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim rests on large-scale simulations determining a sequence of transitions (isotropic \to bands \to cross-sea \to homogeneous polar \to micro-clustered) as a function of alignment rate. The formulation is a continuous-time Langevin dynamics with finite relaxation rate toward local mean orientation, but the phase diagram is extracted from finite boxes without reported finite-size scaling, Binder cumulant crossings at multiple L, or checks that band wavelengths and cross-sea intersections remain stable under doubling of linear size. In Vicsek-like models, such structures are known to be sensitive to periodic boundaries and system size; the reported first-order character and non-monotonic band-size dependence could therefore be contaminated by finite-L artifacts rather than reflecting the true thermodynamic phases.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript introduces a Langevin formulation of Vicsek-like active particles in which orientations relax at finite rate toward the local mean direction (controlled by alignment strength J and rotational diffusivity Dr). Large-scale simulations are used to determine the nonequilibrium phase diagram versus activity and alignment rate, revealing a sequence of transitions: homogeneous isotropic to polar bands to cross-sea (intersecting bands) to homogeneous polar to micro-clustered. The isotropic-to-polar transition is identified as strongly first-order on the basis of Binder cumulants and bimodal distributions of local polarization and density; band size is reported to depend non-monotonically on alignment rate near onset.","tokens_in":1868,"tokens_out":449,"duration_ms":16772,"significance":"If the reported phase sequence and first-order character survive the thermodynamic limit, the work demonstrates that finite-time orientational relaxation functions as an independent control parameter capable of qualitatively restructuring collective states in polar active matter, producing phases (cross-sea, micro-clustered) absent from instantaneous-alignment models. The explicit use of Binder cumulants to diagnose coexistence and the combination of Vicsek consensus with XY-like rotational dynamics constitute concrete, falsifiable additions to the active-matter literature.","major_comments":[{"comment":"The central phase diagram and the claims of a first-order isotropic-polar transition together with non-monotonic band-size dependence rest on simulations performed in finite periodic boxes. No finite-size scaling analysis, Binder-cumulant crossings evaluated at multiple linear sizes L, or explicit checks that band wavelengths and cross-sea intersection statistics remain invariant under doubling of system size are reported. In Vicsek-like models such structures are known to be sensitive to boundary conditions; without these controls the reported sequence and transition order cannot yet be regarded as thermodynamic.","section":"Numerical methods and phase-diagram results (implicit in the abstract description of large-scale simulations)"}],"minor_comments":[{"comment":"The abstract states that the isotropic-to-polar transition is 'strongly first order' but does not indicate the range of system sizes over which the Binder cumulants and bimodality were observed.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the careful reading of our manuscript and the constructive comments regarding the need to establish thermodynamic-limit behavior. We address the major comment below.","responses":[{"response":"We agree that finite-size scaling analysis, including Binder-cumulant crossings at multiple system sizes and explicit checks of invariance under system-size doubling, is required to confirm that the reported phase sequence and first-order character persist in the thermodynamic limit. The original manuscript relied on large periodic simulation boxes but did not report such scaling studies. In the revised version we will incorporate a dedicated finite-size analysis section, presenting Binder cumulants for several linear sizes L, together with data confirming that band wavelengths and cross-sea statistics remain robust upon doubling the system size. This will directly address the concern about boundary-condition sensitivity.","revision_made":"yes","referee_comment":"[Numerical methods and phase-diagram results (implicit in the abstract description of large-scale simulations)] The central phase diagram and the claims of a first-order isotropic-polar transition together with non-monotonic band-size dependence rest on simulations performed in finite periodic boxes. No finite-size scaling analysis, Binder-cumulant crossings evaluated at multiple linear sizes L, or explicit checks that band wavelengths and cross-sea intersection statistics remain invariant under doubling of system size are reported. In Vicsek-like models such structures are known to be sensitive to boundary conditions; without these controls the reported sequence and transition order cannot yet be regarded as thermodynamic."}],"tokens_in":1377,"tokens_out":315,"duration_ms":22403,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main point is that this paper adds a finite relaxation rate to the orientational dynamics on top of Vicsek local alignment and finds that it drives the system through isotropic, banded, cross-sea, homogeneous polar, and micro-clustered states. That sequence is the concrete new observation.\n\nThe model itself is a straightforward Langevin extension that keeps the consensus rule but lets orientations relax continuously toward the local mean at a tunable rate while adding rotational noise. The simulations are large enough to see the states clearly, and the authors supply Binder cumulants plus bimodal histograms to support a first-order isotropic-polar transition. The non-monotonic band-size dependence on alignment rate is also a specific result that follows from the runs.\n\nThe soft spot is exactly the one flagged in the stress-test note. The phase diagram comes from finite boxes with no reported crossings of Binder cumulants at multiple linear sizes, no doubling checks on band wavelength or cross-sea stability, and no explicit discussion of how the structures behave under periodic boundaries. Vicsek-type models have a long history of size-sensitive bands and clusters, so the claim that relaxation rate qualitatively restructures the phases rests on evidence that could still be contaminated by finite-L effects.\n\nThis work is for people who already follow active-matter phase diagrams and want to see how the details of orientational relaxation change the picture. A reader in that subfield would get a usable set of observations and diagnostics, but would also want the size-dependence questions answered before treating the diagram as settled.\n\nIt is worth sending to peer review. The model extension is clean and the diagnostics are better than average, but any referee will need to press on the numerics.","headline":"Finite relaxation time in a Vicsek-style model produces a reported sequence of phases, but the simulations lack the finite-size scaling needed to confirm they survive in the large-system limit.","tokens_in":2382,"tokens_out":418,"would_cite":false,"duration_ms":14104,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Finite-time orientational relaxation acts as a control parameter that qualitatively restructures collective behavior in polar active matter.","keywords":["polar active matter","orientational relaxation","phase transitions","Vicsek model","collective motion","nonequilibrium phases","Langevin dynamics","active particles"],"falsifier":"A simulation or experiment that fails to produce the predicted sequence of phases, including the cross-sea regime and the strongly first-order character of the isotropic-to-polar transition, when alignment rate is varied at fixed activity.","tokens_in":2613,"feed_emoji":"🔄","tokens_out":513,"duration_ms":15278,"temperature":0.7,"pith_summary":"The paper introduces a Langevin model for Vicsek-like active particles in which orientations relax at finite rate to the local mean direction, controlled by alignment strength J and rotational diffusivity Dr. Large-scale simulations map the nonequilibrium phase diagram as a function of activity and alignment rate, revealing transitions from homogeneous isotropic to polar bands, cross-sea, homogeneous polar, and micro-clustered states. The isotropic-to-polar transition is strongly first-order, shown by Binder cumulants and bimodal distributions indicating gas-liquid coexistence. This establishes finite-time relaxation as a tunable driver of collective states, relevant for systems where alignment occurs over measurable timescales rather than instantaneously.","feed_headline":"Finite relaxation rate drives phase sequence in active matter","feed_subtitle":"Varying alignment timescale in simulations yields isotropic, banded, cross-sea, polar, and micro-clustered states.","key_machinery":"Langevin formulation of Vicsek-like particles with finite-rate relaxation toward the local mean direction, combining local consensus with XY-like orientational dynamics via alignment strength J and rotational diffusivity Dr.","core_discovery":"Increasing the alignment rate drives a sequence of transitions from a homogeneous isotropic state to polar bands, a cross-sea phase of intersecting bands, a homogeneous polar state, and ultimately a micro-clustered regime. The isotropic-to-polar transition is strongly first order, as evidenced by Binder cumulants and bimodal distributions of local polarization and density, indicating coexistence of gas-like and liquid-like regions. Near the onset of collective motion, band size increases with activity but depends non-monotonically on alignment rate.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Alignment rate reorders active matter phases","Finite relaxation sequences polar states in matter","Orientation dynamics drive phase transitions in active matter","Relaxation rate yields isotropic to micro-clustered phases"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"The introduced Langevin formulation with finite-rate relaxation toward local mean direction, together with the large-scale simulations, is sufficient to determine the nonequilibrium phase diagram without artifacts from finite system size or other numerical limitations.","fun_headline_variants_meta":{"raw":{"variants":["Alignment rate reorders active matter phases","Finite relaxation sequences polar states in matter","Orientation dynamics drive phase transitions in active matter","Relaxation rate yields isotropic to micro-clustered phases"]},"model":"grok-4.3","cost_usd":0.00431,"raw_usage":{"total_tokens":2164,"prompt_tokens":665,"num_sources_used":0,"completion_tokens":53,"cost_in_usd_ticks":43099500,"prompt_tokens_details":{"text_tokens":665,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1446,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":665,"tokens_out":53,"duration_ms":12973,"temperature":1.0,"reasoning_tokens":1446,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-27T11:49:24.552108+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A simulation or experiment that fails to produce the predicted sequence of phases, including the cross-sea regime and the strongly first-order character of the isotropic-to-polar transition, when alignment rate is varied at fixed activity.","supporting_citations":[],"review_version":1}