{"id":"0fbd0c0b-0591-46f5-a95a-53b54e62813f","arxiv_id":"2608.11041","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"In an active exclusion process with hole-dependent hopping, increasing activity (lower switching rate) suppresses jamming and eventually eliminates the jammed phase entirely.","lead":"This paper studies a one-dimensional model of self-propelled particles on a ring that can switch direction, and it finds that activity destabilizes the low-density jammed state of the passive model. The result maps how the jamming phase boundary moves as particles become more active, which matters for designing active materials and for theories of nonequilibrium phase transitions.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Activity-inhibits-jamming claim rests on a mobility threshold and on excluding the low-density data where a jam would first appear; the phase diagram is not demonstrative for γ<1.","rationale":"The reader's weakest-assumption analysis identifies the same concern I consider most load-bearing: the phase boundary is located by hand-chosen mobility thresholds, finite-size effects near the threshold are acknowledged, and the key low-density data near γ ≈ 1 are excluded. The paper itself flags the missing rigorous mobility bound in Sec. VII, and Sec. III states that the excluded low-density data 'likely suffers from finite size effects.' That is not an internal contradiction, but it leaves the central qualitative claim—that activity can eliminate the jammed phase entirely for sufficiently small γ—without decisive support. The scaling theory in Sec. V actually sharpens the worry: Eq. (19a) says w ≈ 1 − B(b)ρ/γ for ρ ≪ γ, meaning that for any fixed γ one must probe very small ρ to distinguish a true jammed phase (extensive hole cluster, w = 1 in the thermodynamic limit) from a fluid whose mobility merely approaches 1 as ρ → 0. Because the plotted phase diagram uses w = 0.99 as the criterion and does not test the hole-cluster extensivity at the relevant low densities, the no-jam region for γ < 1 could be an artifact of not going to low enough density or large enough system size. I do not see a reason to move the verdict to REJECT: the paper's simulations, mean-field integrations, and perturbation theories are mutually consistent in the regimes they do cover, and the scaling prediction w_s ~ 4/s is a useful analytic result. The honest position is exactly CONDITIONAL, as the reader concluded, because a targeted simulation at lower density and larger system size could settle whether the claimed elimination of the jammed phase is real or merely a shift to densities below the numerical resolution. Thus the verdict remains unchanged.","tokens_in":19365,"tokens_out":5267,"duration_ms":49949,"concrete_test":"Run Monte Carlo at γ = 0.5 and γ = 0.1 for ρ = 0.02, 0.01, 0.005 with L = 2048, 4096, 8192, measuring w and the largest-hole-cluster fraction ⟨hmax⟩/L. If ⟨hmax⟩/L extrapolates to a positive value as L → ∞, or if w tends to 1 together with an extensive cluster, then the fluid-only conclusion for γ < 1 is false. If ⟨hmax⟩/L → 0 and w remains strictly below 1 for all ρ > 0, the conclusion is supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The phase boundary in Fig. 1d is defined by the maximum density where the mean mobility is 0.99 (Monte Carlo) and 1.003 (mean field), and Sec. III explicitly excludes low-density data near γ≈1 as unreliable. This is load-bearing because the scaling result Eq. (19a) gives w ≈ 1 − B(b)ρ/γ for ρ ≪ γ, so for any fixed γ < 1 the mobility tends toward 1 as ρ decreases; the only thing preventing a threshold crossing is finite-size effects or an unmeasured macroscopic hole cluster. The thermodynamic distinction between fluid and jammed phases is not w = 0.99 versus 0.98 but whether a hole cluster is extensive. The paper admits in Sec. VII that it has not rigorously shown w ≤ 1 in the jammed phase, so the plotted boundary could be an artifact of the mobility cutoff. If at γ < 1 there is a finite-density, extensive-hole-cluster phase with w below 1, the headline claim that activity can eliminate jamming fails; the data currently exclude exactly the densities needed to rule this out.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper studies a one-dimensional lattice gas of hard-core particles with an internal ±1 orientation that flips at rate γ; a particle hops into a neighboring hole in its orientation direction with rate u_n = u_∞(1 + b/n), b > 2. In the passive limit γ → ∞ this reduces to a known exclusion process with a jamming transition at density ρ_c = (b−2)/(b−1). Using Monte Carlo simulations, numerical integration of a mean-field closure, and perturbation theory, the authors report that finite switching activity moves the critical density downward, that for sufficiently small γ the mobility never reaches one so the system remains fluid at all densities, and that in the low-density, low-γ scaling limit the mobility has the universal form w ≈ 4γ/ρ for ρ ≫ γ. The paper also presents hole-cluster distributions and largest-cluster statistics supporting a change of cluster structure with γ.","tokens_in":19515,"tokens_out":8273,"duration_ms":77514,"significance":"If the central claim is correct, the paper makes a clean conceptual point: activity does not merely shift the canonical jamming transition but can remove it, with a phase diagram in the (γ, ρ) plane and a nontrivial low-density scaling regime. The manuscript is careful in several respects: the passive limit is reviewed in Appendix A, the large-γ perturbation is solved against boundary conditions in Appendix E, the small-γ scaling is derived from mean-field generating functions in Appendix F, and the universal 4/s mobility is checked against the exact b=0 solution and against simulations and mean-field numerics in Fig. 3. These internal consistencies make the analytical framework credible. The main reservation is that the headline phase boundary for γ < 1 rests on arbitrary mobility thresholds and on a region of the phase diagram from which the most relevant data are excluded, so the claim that activity can eliminate jamming is not yet demonstrated at the same level as the scaling results.","major_comments":[{"comment":"The central claim that the system remains fluid for all densities when γ < 1 is based on the criterion that the phase boundary is the maximum density at which the mobility equals 0.99 (Monte Carlo) or 1.003 (mean field), and the text states that low-density data near γ ≈ 1 are excluded as unreliable. This is exactly the region that matters, because Eq. (19a) predicts w ≈ 1 − B(b)ρ/γ for ρ ≪ γ; for any γ < 1 the mobility will approach 1 as ρ decreases, and finite-size effects can prevent the threshold from being crossed even if a jammed state exists. The authors should either present a system-size-scaling analysis of the hole-cluster distribution or of ⟨h_max⟩ in the low-density region, or otherwise prove that no extensive hole cluster appears for γ < 1, before the activity-inhibits-jamming conclusion can be regarded as established.","section":"Sec. III, Fig. 1d"},{"comment":"The paper explicitly states that it has not rigorously shown that the mobility is bounded above by one in the jammed phase. This is load-bearing because the passive jammed phase is identified precisely by w = 1, and the argument that γ < 1 has no jammed phase assumes that a jammed phase would make the mobility reach the threshold. If a jammed phase with w < 1 existed, Figs. 1a and 1d would not distinguish it from the fluid phase. The exponential hole-cluster distributions in Fig. 4 are more direct evidence, but they are shown for one density (ρ = 0.125) and one b (2.5); a quantitative test of extensivity of the largest hole cluster as a function of L, at several densities below ρ = γ, is needed to close this gap.","section":"Sec. VII"},{"comment":"The Monte Carlo data are presented without error bars or numbers of independent runs, and the mean-field curves are obtained from a single truncation n_max = 1024. Since the phase boundary is read off a mobility threshold at the 1% level, the statistical and truncation uncertainties are of the same order as the effect used to define ρ_c; in fact, the overshoot of the mobility above 1 noted in Sec. III shows that O(1%) finite-size deviations are present. The authors should provide error bars, a system-size dependence for the threshold density, and a check that the mean-field boundary is stable with respect to n_max.","section":"Sec. III, Figs. 1a-1d"}],"minor_comments":[{"comment":"There are several typographical and ligature artifacts (e.g., 'sufficiently' in the Abstract) that should be cleaned before publication.","section":"Abstract"},{"comment":"The Euler constant is denoted γ_e, which is easily confused with the switching rate γ; a different symbol such as γ_E would avoid ambiguity.","section":"Appendix E, Eq. (E.9)"},{"comment":"The crossover line ρ = γ is drawn in the same panel as the jammed/fluid boundary; since the paper itself describes ρ = γ as a demarcation of passive-fluid and active-fluid behavior rather than a phase transition, using a dashed or shaded line with an explicit 'crossover' label would prevent misinterpretation.","section":"Eq. (19) and Fig. 1d"},{"comment":"The definition P(n) = Σ_{α,β} P^{αβ}_n appears only in the caption; the panel legend 'size distribution of clusters' could be made more explicit by stating the summation directly in the panel.","section":"Fig. 4(a)"}],"recommendation":"major_revision","confidential_remarks":"For the editor: the manuscript is within the journal's scope and the analytical machinery is sound, but the headline phase-diagram claim is currently supported mainly by threshold-based numerics with no error bars and with the most relevant low-density data for γ < 1 excluded. I would encourage a revision that adds finite-size scaling of the cluster-size distribution in the γ < 1 region; with that addition the paper could be publishable. No concerns about attribution or overlap."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Here's the short version: this is a solid within-subfield paper that probably does what it claims, but the headline claim \"activity can inhibit jamming\" is a bit ahead of the evidence. The genuinely new results are the phase diagram showing rho_c decreasing with gamma and disappearing below a threshold, and the asymptotic mobility scaling w_s ~ 4/s in the low-density/high-activity limit. The 4/s result is analytic for the mean-field model and holds for all b >= 0, including b = 0 where an exact solution exists; simulations and numerical integration of the mean-field equations collapse onto it. The large-gamma perturbation theory is worked out carefully and matches the numerical data in the fluid phase. The paper is self-contained: passive limit, generating function derivations, and both perturbation expansions are in the appendices, and nothing seems circular.\n\nThe soft spots are real but not fatal. The phase boundary is defined by mobility thresholds (0.99 in Monte Carlo, 1.003 in mean field) rather than a true thermodynamic criterion; only two system sizes are used; and the low-density data near gamma = 1 are explicitly excluded as unreliable. More importantly, the paper concedes in Sec. VII that it has not rigorously shown w <= 1 in the jammed phase. The stress-test note is right that for gamma < 1 and small rho, Eq. (19a) gives w approaching 1 from below, so a threshold crossing is only prevented by finite-size effects or an unmeasured macroscopic hole cluster. If a finite-density jammed phase with w < 1 exists at small gamma, the \"eliminate jamming\" claim fails. The paper's own language is actually more careful than the abstract—\"strongly suggest\" is used in Sec. VII. So I would call this a conditional accept rather than a clean one: the central physics is credible, but the phase boundary for gamma < 1 is not pinned down.\n\nWho should read it: people working on active ZRP/condensation transitions, and anyone testing mean-field approximations for driven exclusion processes. It deserves a serious referee; the issues are clearly addressable with larger systems, better boundary criteria, or a rigorous bound on mobility.","headline":"A credible, well-analyzed study showing activity can suppress the jamming transition in a 1D active exclusion process, though the 'eliminate jamming' claim rests on a mobility cutoff and excluded low-density data.","tokens_in":20116,"tokens_out":2336,"would_cite":true,"duration_ms":22046,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Adding run-and-tumble self-propulsion to a one-dimensional hard-core particle gas suppresses the jamming transition and, for slow enough orientation flips, removes the jammed phase entirely.","keywords":["jamming transition","active matter","exclusion process","run-and-tumble particles","mean field theory","mobility","hole clusters","zero-range process"],"falsifier":"Simulate rings of length $L=1024$, $2048$, and $4096$ at $b=2.5$, $\\gamma=0.5$, and densities $\\rho=0.02,\\dots,0.30$. If $w(\\rho)$ approaches 1 from below as $L$ grows at any density below the reported boundary, or if the hole-cluster distribution develops a macroscopic component, then a jammed phase exists at small $\\gamma$ and activity does not eliminate jamming; if $w$ stays strictly below 1 and the distribution stays exponential, the claim survives. An analytic proof that $w\\le 1$ in the active jammed phase would replace the numerical thresholds and settle the boundary criterion.","tokens_in":19081,"feed_emoji":"🚧","tokens_out":9526,"duration_ms":81450,"temperature":0.7,"pith_summary":"The paper studies a one-dimensional exclusion process whose hard-core particles carry a self-propulsion direction, $\\eta=\\pm 1$, that flips at rate $\\gamma$. With hop rate $u_n = u_\\infty(1 + b/n)$ for $b>2$, the passive limit $\\gamma\\to\\infty$ is a known jamming transition between a low-density jammed phase with a macroscopic hole cluster and a high-density fluid phase. The paper's main claim is that finite activity pushes the critical density downward and that for sufficiently small $\\gamma$ the jammed phase disappears entirely, leaving only the fluid phase. This matters because it shows activity does not merely shift a nonequilibrium transition; it can destroy it.","feed_headline":"Self-propulsion can erase a jamming transition","feed_subtitle":"Frequent flips keep the passive jam; rare flips keep the system fluid at every density.","key_machinery":"The load-bearing object is the mean mobility $w$, defined as twice the mean hop rate per particle, which takes the value 1 in the jammed phase and values below 1 in the fluid phase; the phase boundary is read off from where $w$ crosses one. The companion objects are the hole-cluster distributions $P^{\\alpha\\beta}_n$ for boundaries of type $\\alpha,\\beta=\\pm 1$, whose generating functions obey a system of mean-field equations that the paper closes by numerical integration or by perturbation theory. The mechanism the paper identifies is a competition between hopping and orientation switching: at large $\\gamma$, particles tumble before they can execute a directed hop, recovering the passive kinetics; at small $\\gamma$, a particle at the edge of a hole cluster hops in its own direction before tumbling, and the jam is destabilized.","core_discovery":"Working with Monte Carlo simulations and a mean-field closure, the paper argues that the jamming transition of the passive model survives only above a switching-rate threshold. For $b=2.5$ and $u_\\infty=0.1$, the measured phase boundary in the $\\gamma$--$\\rho$ plane ends near $\\gamma\\approx 1$: for smaller $\\gamma$ the mean mobility $w$ never reaches one, so the system is fluid at all densities, while for larger $\\gamma$ the critical density $\\rho_c$ lies below the passive value $r_c=(b-2)/(b-1)$ and decreases as $\\gamma$ decreases. In the fluid phase the active mobility is smaller than the passive mobility at the same density, with the difference decaying as $\\gamma^{-1}$ at large $\\gamma$. In the double limit $\\rho,\\gamma\\to 0$ at fixed $s=\\rho/\\gamma$, the mobility is $w_s\\approx 1-B(b)\\rho/\\gamma$ for $s\\ll 1$ and $w_s\\approx 4/s$ for $s\\gg 1$, independent of $b$; and the hole-cluster size distribution becomes exponential at small $\\gamma$, the hallmark of a fluid.","pith_inferences":["An implication the paper leaves implicit is that the same boundary-hopping mechanism should weaken condensation in other zero-range-type models: any directed move that can occur before a flip attacks the jam boundary, so activity may generically suppress rather than merely shift such transitions.","The paper uses the line $\\rho=\\gamma$ to separate passive-fluid from active-fluid behavior; a natural test is whether this is a genuine sharp transition or a smooth crossover as $L$ grows.","The universal $4/s$ mobility tail for $s\\gg 1$ hints at a scaling law tied to the absorbing $\\gamma=0$ state; checking hop-rate families such as $u_n=u_\\infty(1+b/n^\\nu)$ would show whether the exponent is universal.","The mobility overshoot above 1 near the reported threshold is attributed to finite size; if a rigorous upper bound $w\\le 1$ in the jammed phase were established, the threshold estimate could be replaced by an exact boundary."],"forward_implications":["For fixed $b>2$ there is a finite switching threshold below which no jammed phase exists at any density; for $b=2.5$ the data place it near $\\gamma\\approx 1$.","Above that threshold the critical density obeys $\\rho_c(\\gamma)