{"id":"36ecdb7a-b073-45da-9c3f-b96d36ac5baa","arxiv_id":"2607.16460","paper_version":1,"verdict":"REJECT","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"high","formal_verification":"none","parameter_count":6,"one_line_summary":"Sheared glass-forming liquids relax faster because shear suppresses stringlike cooperative motion, and the relaxation time is claimed to obey the equilibrium String Model with an effective temperature.","lead":"Simulations show that shearing a glass-forming liquid shrinks the cooperative 'string' motions that make it sluggish, greatly speeding up relaxation. The paper argues the same string-based rule describes resting and sheared liquids if the bath temperature is replaced by a shear-dependent effective temperature.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Eq. (3)'s 'parameter-free prediction' is not actually made: Tmap is defined by Eq. (2) from the very τα that Eq. (3) is said to predict, and the independently measured Tavg,c is never inserted into Eq. (3).","rationale":"The reader's verdict identifies the same fundamental weakness: the 'prediction' of nonequilibrium relaxation times is based on an effective temperature that is defined from the very quantity being predicted. My load-bearing concern is essentially the circularity of Eq. (2) and Eq. (3), and the fact that the only truly independent temperature (Tavg,c from the FDR) is not used in the predictive formula. The reader's weakest_assumption focuses on the adequacy of a single scalar effective temperature; that is a related but distinct physical concern. I partially agree because the reader's rationale does explicitly state the circularity and the non-use of Tavg,c, even though the weakest_assumption field emphasizes the scalar-temperature sufficiency. The paper contains solid simulation evidence for shear suppression of strings and a novel FDR crossing-point construction, but those do not rescue the central quantitative claim. A concrete computational test—inserting Tavg,c into Eq. (3) without invoking Eq. (2)—would settle whether the theory is genuinely predictive. Until that test is done and passes, rejection is warranted.","tokens_in":25658,"tokens_out":7445,"duration_ms":67360,"concrete_test":"Re-analyze Fig. 3(d) using Tavg,c (from the crossing-point FDR) instead of Tmap: for each (T, γ) state point, compute the predicted ln(τα/τ0) = (ΔH0 − Tavg,c ΔS0) z(T,γ)/(kB Tavg,c) using the same measured z(T,γ) and equilibrium parameters, and compare to the simulated ln(τα/τ0). Do not use Eq. (2) anywhere. If the predicted and simulated τα do not agree within the plotted scatter across all three systems and shear rates, the central claim of an independent parameter-free prediction fails. A complementary check is to directly compare z(T,γ) with z_eq(Tmap) for all state points; equality is necessary for Eq. (3) to be consistent with the Tmap-based collapse.","verdict_should_be":"REJECT","load_bearing_attack":"The central quantitative claim—that Eq. (3) predicts nonequilibrium τα without additional fitting parameters—is undercut by the way Tmap is defined. Equation (2) imposes τα(Tmap, γ=0) = τα(T, γ), so Tmap is constructed to reproduce the driven relaxation time. Substituting Eq. (3) shows that the prediction is equivalent to requiring z(T, γ) = z_eq(Tmap), where z_eq is the equilibrium string-length ratio. The paper never directly tests this equality; instead, Fig. 3(d) plots simulated ln(τα/τ0) against an x-axis built using the same simulated τα through Tmap, so the collapse is at least partly tautological. The FDR-derived Tavg,c agrees with Tmap in Fig. 4(c), but it is not used as the effective temperature in Eq. (3); therefore the 'independently determined' claim is not demonstrated. Moreover, SI §S4.3 (Fig. S9) states that Fs(q,t) and ⟨s(t)⟩ under shear differ noticeably from equilibrium at Tmap, implying z(T,γ) ≠ z_eq(Tmap) and raising doubt that the collapse in Fig. 3(d) can be genuine. The SI also flags the standard FDR perturbation protocol as problematic for Poly-P (§S4.1), yet Poly-P is included in the central collapse. A revised test using Tavg,c directly in Eq. (3) is needed.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript proposes a unified microscopic theory of relaxation in equilibrium and shear-driven glass-forming liquids. Using molecular dynamics simulations of KABLJ, a constant-volume polymer melt, and a constant-pressure polymer melt, it shows that steady shear suppresses stringlike cooperative motion and shortens the structural relaxation time. The authors extend the equilibrium String Model by introducing an effective temperature Tmap, defined in Eq. (2) as the equilibrium temperature at which the equilibrium relaxation time equals the driven-system relaxation time, and by inserting this Tmap together with the measured shear-dependent string length z(T) into Eq. (3). They claim that Eq. (3) gives a parameter-free, quantitative prediction of the nonequilibrium relaxation time. They also construct an FDR-based effective temperature Tavg,c, report agreement with Tmap, and conclude that equilibrium and nonequilibrium relaxation are governed by the same cooperative mechanism. The supplementary information documents the simulation protocol, FDR calculations, and additional comparisons.","tokens_in":26020,"tokens_out":6006,"duration_ms":54006,"significance":"The idea that a single scalar effective temperature, combined with the measured extent of collective motion, can collapse both equilibrium and sheared relaxation onto one String-Model curve is attractive and, if established, would be an important step for driven glassy systems. The paper's strengths are the breadth of systems studied, the careful validation of the FDR implementation against the literature (SI Fig. S5), and the explicit construction of a crossing-based FDR analysis. However, the central claim as presented is not supported: Tmap is defined through the very relaxation time that Eq. (3) claims to predict, so the collapse in Fig. 3(d) is at least partially a consistency check rather than an independent prediction. The underlying simulation data and FDR machinery are valuable, and a revised version with a genuinely independent test could make a strong contribution.","major_comments":[{"comment":"The central claim of a parameter-free prediction is not established. Equation (2) defines Tmap via τα(Tmap,γ=0)=τα(T,γ), so Tmap is constructed from the simulated relaxation time that Eq. (3) is alleged to predict. Substituting Eq. (3) shows that the prediction reduces to z(T,γ)=z_eq(Tmap), where z_eq is the equilibrium string-length ratio at Tmap. This equality is never directly tested. In Fig. 3(d), the x-axis is built from the same simulated τα through Tmap, and the y-axis is the same simulated τα; the collapse is therefore at least partly tautological. A direct test using the independently determined Tavg,c in Eq. (3), or a direct comparison of z(T,γ) with z_eq(Tmap), is required before the claim 'without any additional nonequilibrium fitting parameters' can be accepted.","section":"A Predictive Theory (Eqs. 2-3; Fig. 3d)"},{"comment":"Supplementary Fig. S9 shows that the full sheared Fs(q,t) and the sheared ⟨s(t)⟩ differ noticeably from their equilibrium counterparts at Tmap, even though τα is matched by construction. Since Eq. (3) uses the measured shear-dependent z(T,γ), and since z_eq(Tmap) is the only string-length ratio consistent with Eq. (2), Fig. S9 raises the question of how the collapse in Fig. 3(d) is obtained. If the difference in the characteristic string length L is quantitatively negligible, that should be shown with error bars. If it is not negligible, the collapse cannot be interpreted as evidence for Eq. (3). This figure also directly undermines the assumption that a single scalar effective temperature fully characterizes the driven state for relaxation.","section":"SI §S4.3, Fig. S9"},{"comment":"The abstract states that the effective temperature is 'independently determined from fluctuation-dissipation relations' and that the theory quantitatively predicts τα. However, Tavg,c is only shown to agree with Tmap in Fig. 4(c); it is never inserted into Eq. (3). Agreement between Tavg,c and Tmap, even if quantitative, does not demonstrate that Eq. (3) predicts τα when Tavg,c is used. The authors should provide the direct test—compute Eq. (3) with Tavg,c in place of Tmap—and report the resulting scatter for each system, temperature, and shear rate. Without this step, the 'independently determined' claim is not demonstrated.","section":"Effective Temperature from FDR; Fig. 4(c)"},{"comment":"The SI states that for the Poly-P system the standard FDR perturbation protocol 'becomes problematic under isobaric conditions' and that the FDR exhibits non-monotonic behavior. Yet Poly-P is included in the central collapse of Fig. 3(d). If the FDR-derived Tavg,c is intended to provide the independent grounding of Tmap, the authors need to establish that Tavg,c for Poly-P is reliable despite this concern, or explicitly exclude Poly-P from the 'independently determined' claim. As written, the connection between Tmap and Tavg,c for one of the three central systems is not firm.","section":"SI §S4.1, Poly-P FDR"}],"minor_comments":[{"comment":"The figure has no error bars. Given the circular construction of Tmap, error bars on z(T,γ), L, and Tmap are essential for judging whether the collapse is meaningful.","section":"Fig. 3(d)"},{"comment":"The activation entropy ΔS0 for Poly-V is positive, unlike the other two systems. A brief physical comment would help the reader interpret this difference.","section":"Table I"},{"comment":"The notation z(T) is used for both the equilibrium and nonequilibrium string-length ratio. Explicitly writing z(T,γ) for the sheared case would avoid ambiguity, especially in the context of Eq. (2).","section":"Notation, Eq. (3)"},{"comment":"The sentence in the text immediately following Eq. (3) says the relaxation time 'is predicted without introducing any additional fitting parameters,' but because Tmap is defined from τα, this phrasing is misleading. Rephrase to acknowledge that Tmap is a mapping quantity until an independent determination is used.","section":"General text"},{"comment":"The term 'effective disorder temperature' is used without a citation to the original literature. Adding reference(s) would improve the scholarly context.","section":"Discussion of Tavg"}],"recommendation":"major_revision","confidential_remarks":"This is a close call. The simulation data and the FDR-based construction are valuable, but the central claim of a parameter-free prediction is not supported as written because Tmap is defined from the very quantity Eq. (3) claims to predict. The required analysis—inserting the independently measured Tavg,c into Eq. (3), or directly testing z(T,γ)=z_eq(Tmap)—is within the scope of the existing simulations and supplementary data. If that test succeeds, the paper could make a strong contribution; if it fails, the paper should be substantially reframed as an empirical correlation, which would lower its significance. I therefore recommend major revision rather than outright rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Here's my take. The crossing-point fluctuation-dissipation construction is genuinely new: sheared and equilibrium Fs(q,t) curves are intersected to build a chi-Fs plot, and the resulting Tavg_c is a clever way to define an effective temperature. The shear suppression of stringlike cooperative motion is well documented across three model systems, and the authors honestly show that simply replacing the equilibrium string length with the driven one fails, which motivates the effective-temperature idea. The simulation work itself is careful and reproducible.\n\nThe central claim, though, is overstated. Eq. (3) is presented as a prediction of tau_alpha under shear, but Tmap is defined in Eq. (2) as the equilibrium temperature whose tau_alpha equals the driven tau_alpha. You cannot compute Tmap without already knowing the quantity you want to predict. So Fig. 3(d) is best read as a consistency check: does the driven string length z(T,gamma) equal z_eq(Tmap)? The collapse depends on that equality, which the paper never directly tests. The independently derived Tavg_c is shown to approximate Tmap, but it is never plugged into Eq. (3) to produce a predicted tau_alpha. That is the missing test. Without it, the phrase 'independently determined from fluctuation-dissipation relations quantitatively predicts' is not supported.\n\nThere are compounding problems. SI Fig. S9 shows that neither Fs(q,t) nor <s(t)> under shear matches equilibrium at Tmap; only tau_alpha matches, by construction. So the equality z(T,gamma)=z_eq(Tmap) is doubtful, and the clean collapse in Fig. 3(d) is not explained. The SI also flags the standard FDR perturbation protocol as problematic for Poly-P, yet Poly-P appears in the central collapse and in the Tavg_c comparison. The reduction of a driven state to a single scalar effective temperature is approximate at best.\n\nNone of this kills the qualitative message: shear suppresses strings, and an effective temperature helps organize the data. But the quantitative 'unified theory' claim is not established. The fix is straightforward: use Tavg_c directly in Eq. (3), plot predicted versus simulated tau_alpha, and test z(T,gamma)=z_eq(Tavg_c) explicitly. If that works, it would be a strong paper. As it stands, it deserves a serious referee and major revision, not a desk reject. I'd engage with it and would want to see the revised version before citing the prediction.","headline":"Solid simulation study with a genuinely new FDR crossing-point construction, but the 'parameter-free prediction' of relaxation under shear is built on a circular Tmap definition, and the independent Tavg_c is never used to make the prediction.","tokens_in":699,"tokens_out":1116,"would_cite":true,"duration_ms":54787,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Sheared and equilibrium glass relaxation follow the same string-based law once a single effective temperature replaces the bath temperature.","keywords":["glass transition","structural relaxation","steady shear","stringlike cooperative motion","effective temperature","fluctuation-dissipation relation","String Model","nonequilibrium dynamics"],"falsifier":"Measure the sheared system's mean-square displacement or diffusion constant at several T and γ̇, compute T_map from τα matching, and check whether D(T,γ̇) collapses onto D_eq(T_map). If the collapse fails by more than the uncertainty, the single-scalar reduction is approximate. Alternatively, find a state where the crossing-point χ–F plot is not linear, so T_avg,c is undefined.","tokens_in":25501,"feed_emoji":"🧪","tokens_out":4172,"duration_ms":36244,"temperature":0.7,"pith_summary":"The paper tries to prove that structural relaxation in glass-forming liquids under steady shear is not a separate phenomenon from equilibrium relaxation: the same stringlike cooperative rearrangements control both, and a single scalar effective temperature captures the effect of driving. With that temperature, the equilibrium String Model predicts relaxation times across all simulated temperatures and shear rates using zero new fitting parameters. The authors show that modifying only the cooperative-motion factor fails, and that the needed effective temperature is not the usual long-time FDR slope but an average over all timescales obtained from crossing points between the sheared and equilibrium correlation functions. If right, this gives a unified microscopic account of thermal and mechanical activation in glass-formers.","feed_headline":"One effective temperature unifies sheared and equilibrium glass relaxation","feed_subtitle":"Stringlike cooperative motion plus a shear-mapped temperature predicts simulated relaxation times with zero new parameters.","key_machinery":"The central object is the Generalized String Model relation τα = τ0 exp[(ΔH0 − T_map ΔS0) z(T)/(k_B T_map)], where z(T) is the characteristic string length normalized by its onset-temperature value and T_map is an effective temperature. The paper identifies T_map with T_avg,c, obtained from the crossing-point fluctuation-dissipation analysis: the long-time intercept of the parametric plot of susceptibility versus correlation built from intersections of the sheared Fs(q,t) with equilibrium curves. This construction does the work of converting the driven system's thermodynamics into an equilibrium-looking description without adjustable parameters.","core_discovery":"External driving suppresses stringlike cooperative motion, and this suppression alone cannot explain the accelerated relaxation. The paper's central claim is that the equilibrium String Model remains valid under shear provided the bath temperature T is replaced by an effective temperature T_map, defined as the equilibrium temperature at which the relaxation time matches the driven system's. They further derive T_map from a generalized fluctuation-dissipation construction: the sheared intermediate scattering function is intersected with a family of equilibrium curves, and the intercept of the resulting parametric χ–F plot yields T_avg,c, which coincides with T_map. Inserting T_avg,c and the s","pith_inferences":["If this holds, the crossing-point FDR procedure could serve as a standard operational definition of effective temperature in sheared materials, potentially extendable to experimental colloidal systems where both Fs and susceptibility are measurable.","The paper's own S9 shows the full Fs(q,t) shape under shear differs from equilibrium at T_map; so the single-scalar mapping is a coarse-graining of the dynamics, and quantities that depend on non-universal shape (e.g., stretching exponent) may need a distribution of effective temperatures.","A sharper test would be to predict the shear-dependent diffusion coefficient or viscosity using the same T_map and see whether the data collapse as well as τα does; failure there would reveal the limit of the reduction."],"forward_implications":["Relaxation under steady shear is predicted from equilibrium parameters once the effective temperature is measured, enabling parameter-free estimates in processing models.","The failure of T_slow shows that for driven systems the relevant effective temperature is the full-spectrum average, not the asymptotic slow-mode slope, because shear couples time scales.","The same framework is expected by the authors to generalize to other nonequilibrium protocols such as aging and oscillatory driving.","Since T_avg,c equals the phenomenological T_map, it provides a first-principles route to effective temperatures previously introduced ad hoc in rheology."],"fun_headline_variants":["Shear maps temperature to unify glass relaxation","Same cooperative motion, new effective temperature","One temperature predicts sheared glass dynamics","String motion suppression plus effective T explains shear","Effective temperature links equilibrium and sheared glass"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The driven system's relaxation is fully characterized by a single scalar effective temperature T_map, even though the paper's own data show the time-dependent correlation function and string length under shear do not match equilibrium at T_map.","fun_headline_variants_meta":{"raw":{"variants":["Shear maps temperature to unify glass relaxation","Same cooperative motion, new effective temperature","One temperature predicts sheared glass dynamics","String motion suppression plus effective T explains shear","Effective temperature links equilibrium and sheared glass"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":9.9e-05,"raw_usage":{"total_tokens":798,"prompt_tokens":636,"completion_tokens":162,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":380,"completion_tokens_details":{"reasoning_tokens":97}},"tokens_in":380,"tokens_out":162,"duration_ms":2675,"temperature":1.0,"reasoning_tokens":97,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-01T20:53:56.633114+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the sheared system's mean-square displacement or diffusion constant at several T and γ̇, compute T_map from τα matching, and check whether D(T,γ̇) collapses onto D_eq(T_map). If the collapse fails by more than the uncertainty, the single-scalar reduction is approximate. Alternatively, find a state where the crossing-point χ–F plot is not linear, so T_avg,c is undefined.","supporting_citations":[],"review_version":1}