{"id":"48bcbb76-3cf3-483a-af32-a0858d4bfaae","arxiv_id":"2606.01752","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":4.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":2,"one_line_summary":"Simulations show tension-suppressed severing delays stress relaxation and shifts rigidity transition to lower connectivity while tension-enhanced severing accelerates relaxation and shifts it to higher connectivity.","lead":"This paper uses 2D lattice simulations to model how force-dependent stochastic severing affects stress relaxation and rigidity transitions in fiber networks. A smart generalist might read it to understand mechanisms that could influence mechanical stability in biological tissues or engineered materials under strain.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.3","headline":"2D triangular lattice may not capture 3D rigidity shifts under force-dependent severing","rationale":"The reader's weakest_assumption already isolates the 2D-to-3D representativeness issue as load-bearing for the biological claim. Full-text access does not remove this; it only confirms the simulations are 2D. No other internal inconsistency (e.g., in the rate functional form or lattice mechanics) appears more central once the dimensionality gap is acknowledged.","tokens_in":1762,"tokens_out":353,"duration_ms":14845,"concrete_test":"Re-run the stress-relaxation protocol and connectivity-sweep on a 3D random fiber network (or FCC lattice) at equivalent mean coordination and shear strain; if the direction or magnitude of the connectivity shift for tension-suppressed vs. enhanced severing changes by more than the reported strain dependence, the 2D-to-3D extrapolation is unreliable.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim rests on observed shifts in the bending-dominated rigidity transition (to lower/higher connectivity) under tension-suppressed vs. tension-enhanced severing. These shifts are demonstrated exclusively on a 2D triangular lattice with central-force plus bending springs. Real biological fiber networks are 3D, where the Maxwell isostatic point is z=6 rather than z=4, and where out-of-plane modes, random cross-link orientations, and possible torsional stiffness alter both the baseline transition and how local tension modulates severing. The functional form of the stochastic rate is not independently derived from 3D mechanics, so the reported strain- and feedback-strength dependence may be an artifact of the 2D topology and periodic boundary conditions.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The paper develops a computational model of stress relaxation in 2D spring and fiber networks subject to stochastic, force-dependent severing. Using triangular-lattice simulations, it reports that tension-suppressed severing delays relaxation and shifts the bending-dominated rigidity transition to lower-than-expected connectivity, whereas tension-enhanced severing accelerates relaxation and shifts the transition to higher connectivity; the magnitude of these shifts depends on applied shear strain and feedback strength.","tokens_in":1921,"tokens_out":346,"duration_ms":25262,"significance":"If the reported shifts are robust, the work supplies a concrete illustration of how local mechanochemical feedback can move a network across a rigidity transition, which is relevant to understanding cytoskeletal and extracellular-matrix mechanics. The absence of any machine-checked proofs, reproducible code, or parameter-free derivations, however, limits the immediate impact.","major_comments":[{"comment":"Abstract: the abstract states simulation outcomes but supplies no implementation details, error analysis, parameter values, or validation against theory or experiment, so the degree to which the data support the stated shifts cannot be assessed.","section":"Abstract"},{"comment":"Abstract / model description: the central claim of connectivity-dependent shifts rests exclusively on 2D triangular-lattice simulations (central-force isostatic point z=4). Real biological networks are three-dimensional (isostatic point z=6) with out-of-plane modes, random cross-link orientations, and possible torsional stiffness; the functional form of the stochastic severing rate is not derived from 3D mechanics, so the reported strain- and feedback-strength dependence may be an artifact of the 2D topology and periodic boundaries.","section":"Abstract"}],"minor_comments":[],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their careful reading and constructive comments. We respond point by point to the major comments and indicate planned revisions.","responses":[{"response":"We agree that the abstract is concise and omits these details. In the revised manuscript we will expand the abstract to reference the key parameter ranges (connectivity z, shear strain, feedback strength) and state that implementation, error analysis, and validation against limiting analytic cases appear in the Methods and Results sections.","revision_made":"yes","referee_comment":"[Abstract] Abstract: the abstract states simulation outcomes but supplies no implementation details, error analysis, parameter values, or validation against theory or experiment, so the degree to which the data support the stated shifts cannot be assessed."},{"response":"The manuscript deliberately employs a 2D triangular lattice to isolate the interplay between force-dependent severing and the central-force isostatic point at z=4. We will add a dedicated paragraph in the Discussion that explicitly acknowledges the limitations of the 2D setting, including the lack of out-of-plane modes and torsional stiffness, and the phenomenological form of the severing rate. While quantitative shifts may differ in 3D, the qualitative mechanism whereby tension-dependent severing displaces the rigidity transition is expected to persist; the results remain robust across the system sizes and boundary conditions examined in 2D.","revision_made":"partial","referee_comment":"[Abstract] Abstract / model description: the central claim of connectivity-dependent shifts rests exclusively on 2D triangular-lattice simulations (central-force isostatic point z=4). Real biological networks are three-dimensional (isostatic point z=6) with out-of-plane modes, random cross-link orientations, and possible torsional stiffness; the functional form of the stochastic severing rate is not derived from 3D mechanics, so the reported strain- and feedback-strength dependence may be an artifact of the 2D topology and periodic boundaries."}],"tokens_in":1371,"tokens_out":425,"duration_ms":33188,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main result is that tension-suppressed severing slows relaxation and moves the bending-dominated rigidity transition to lower connectivity than the no-feedback case, while tension-enhanced severing speeds relaxation and moves the transition to higher connectivity. The size of the shift grows with applied shear strain and feedback strength.\n\nThe work adds explicit stochastic, force-dependent severing to standard fiber-network rigidity models and runs the two limiting cases to quantify the effect on both relaxation and topology. That extension is the concrete addition; earlier studies looked at connectivity or strain thresholds without this feedback loop.\n\nThe simulations are set up on the usual 2D triangular lattice with central-force and bending springs, which makes the baseline comparison straightforward and lets them isolate the feedback effect.\n\nThe clearest limitation is the exclusive use of 2D. Real biological networks are 3D, where the isostatic point sits at coordination 6 rather than 4, out-of-plane modes exist, and cross-link geometry is disordered. Nothing in the reported results tests whether the same rate law produces comparable shifts once those features are included. The functional form of the severing rate is also assumed rather than derived from 3D force balance, so the quantitative dependence on strain and feedback strength could be tied to the 2D periodic setup.\n\nThis is for people who already run fiber-network simulations for cytoskeletal or extracellular-matrix mechanics. It gives a workable way to include mechanochemical feedback and shows that the feedback direction matters for the transition point. The paper is coherent on its own terms and engages the existing rigidity literature, so it deserves peer review. Referees can ask for 3D checks and any available experimental anchors on the rate law.","headline":"The paper shows force-dependent severing shifts rigidity onset in opposite directions in 2D lattice simulations, but the 2D restriction is a real limit on broader claims.","tokens_in":2381,"tokens_out":421,"would_cite":false,"duration_ms":26264,"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":"Tension-dependent severing rates shift the connectivity threshold for rigidity in strained fiber networks.","keywords":["fiber networks","stress relaxation","stochastic severing","force-dependent feedback","rigidity transition","bending-dominated regime","mechanochemical feedback","triangular lattice"],"falsifier":"Measure the connectivity at which the network crosses into bending-dominated response in a physical or simulated network whose severing rate versus force has been independently calibrated; if the observed threshold does not move in the direction and by the amount predicted for the measured feedback strength and strain, the central claim is falsified.","tokens_in":2675,"feed_emoji":"","tokens_out":736,"duration_ms":22331,"temperature":0.7,"pith_summary":"The paper develops a computational model of fiber networks under constant applied strain in which fibers sever stochastically at a rate that depends on local tension. When tension suppresses the severing rate, stress relaxes more slowly and the network enters the bending-dominated regime at lower connectivity than would be expected from the average number of cuts. When tension increases the severing rate, relaxation occurs faster and the transition moves to higher connectivity. The size of these shifts grows with the magnitude of the applied shear strain and the strength of the force feedback. A reader would care because the result shows how local mechanochemical rules can move the mechanical transition point without any change in the mean connectivity.","feed_headline":"Tension feedback on severing shifts network rigidity threshold","feed_subtitle":"Suppressed rates delay relaxation and move the bending regime to lower connectivity than expected from average cuts","key_machinery":"A 2D triangular-lattice model in which each bond severs at a stochastic rate that is a function of the instantaneous tension it carries.","core_discovery":"The limit of tension-suppressed severing delays stress relaxation and shifts the transition into the bending-dominated regime to lower-than-expected connectivity. In contrast, tension-enhanced severing accelerates relaxation and shifts the transition to higher-than-expected connectivity. The magnitude of this shift depends on the applied shear strain and the strength of the feedback.","pith_inferences":["Cells could adjust the mechanical stability of their cytoskeletal networks by changing only the force sensitivity of severing proteins rather than their overall concentration.","The same feedback logic could be used to design synthetic gels whose rigidity under sustained load is tunable by the strain level at which they are held.","Because the shift depends on strain, networks might cross from one regime to another at a critical strain even if connectivity remains fixed.","Whether the 2D lattice results survive in three-dimensional disordered networks remains an open test of the model."],"forward_implications":["Tension-suppressed severing produces slower stress relaxation than tension-independent severing at the same average rate.","The connectivity marking the onset of the bending-dominated regime drops below the tension-independent value under tension-suppressed severing.","Tension-enhanced severing produces faster stress relaxation and raises the connectivity at the bending transition.","Both the relaxation time and the size of the connectivity shift increase with larger applied shear strain.","Stronger force feedback amplifies the displacement of the rigidity threshold in either direction."],"fun_headline_variants":["Tension-suppressed severing lowers rigidity connectivity threshold","Tension-enhanced severing raises network rigidity threshold","Force feedback on severing alters rigidity transition","Stress feedback changes fiber network rigidity threshold"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"The force dependence of the severing rate is assumed to take a form that produces the reported directional shifts, and the 2D triangular lattice is assumed to capture the essential mechanics of real 3D fiber networks.","fun_headline_variants_meta":{"raw":{"variants":["Tension-suppressed severing lowers rigidity connectivity threshold","Tension-enhanced severing raises network rigidity threshold","Force feedback on severing alters rigidity transition","Stress feedback changes fiber network rigidity threshold"]},"model":"grok-4.3","cost_usd":0.004777,"raw_usage":{"total_tokens":2351,"prompt_tokens":665,"num_sources_used":0,"completion_tokens":47,"cost_in_usd_ticks":47774500,"prompt_tokens_details":{"text_tokens":665,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1639,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":665,"tokens_out":47,"duration_ms":13141,"temperature":1.0,"reasoning_tokens":1639,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-28T12:45:47.046152+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"Measure the connectivity at which the network crosses into bending-dominated response in a physical or simulated network whose severing rate versus force has been independently calibrated; if the observed threshold does not move in the direction and by the amount predicted for the measured feedback strength and strain, the central claim is falsified.","supporting_citations":[],"review_version":1}