{"id":"208400b8-12d7-4811-98e1-6d60e9d2b55a","arxiv_id":"1406.3333","paper_version":2,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"In event-by-event viscous hydrodynamics, bulk viscosity counteracts the shear-viscosity suppression of elliptic and higher-order flow harmonics at RHIC, bringing them closer to ideal-hydrodynamic values.","lead":"A hydrodynamic simulation of quark-gluon plasma at RHIC finds that adding bulk viscosity cancels part of the flow-harmonic suppression caused by shear viscosity, pushing predicted flow closer to the ideal-fluid result. If correct, past estimates of the plasma's shear viscosity, which ignored bulk viscosity, may need revision.","discovery_kind":"extension","skeptic_critique":{"model":"selfhosted/deepseek-v4.1-flash","headline":"The abstract's claim is quantitatively supported only in two regimes that lie outside the physically relevant parameter space: 10×ζ/s, where the pion spectrum goes negative and the pT integral is truncated, and ζ/s = η/s = 0.007, far below the accepted η/s.","rationale":"The reader's weakest_assumption correctly identifies the freeze-out δf^Bulk as the soft spot, and the paper does acknowledge the MOM/MH disagreement in Section II D and the conclusions. I agree that this is the load-bearing issue, so my read does not move the verdict. Where I would sharpen the reader's framing: the problem is not merely that two prescriptions disagree, but that the parameter points where the effect is large are exactly the points where the prescriptions are unreliable. Fig. 3's dramatic 10ζ/s curve is computed with a truncated pT integral because the spectrum goes negative, and Section IV C's equal-viscosity demonstration uses ζ/s = η/s = 0.007, well below the η/s the paper otherwise adopts. The dynamical backbone — Tables III–V showing bulk viscosity suppressing π00 and π12 — is genuinely robust and independent of the freeze-out prescription, and the code validation in Appendix A against TECHQM and the Gubser solution is real, external support. So the paper's physics core stands; what is not established is the quantitative magnitude of the flow-harmonic compensation at realistic viscosities. That is a scope limitation the authors largely acknowledge, and it is the right basis for CONDITIONAL rather than a stronger verdict. I would not adjust the reader's verdict, but I would note that the abstract's unqualified phrasing slightly oversells what the two demonstration regimes actually support, and a sentence in the abstract tying the size of the effect to the ζ/s value used would be more accurate without weakening the paper's contribution. No concern about internal inconsistency or circularity arises; the issue is regime of validity, which routes through correctness risk as the reader already classified it. The forward-looking η/s re-evaluation remark is appropriately hedged with 'may' and is not presented as a result, so I do not treat it as a separate concern. The absence of a data comparison is acknowledged in the conclusions and is a scope choice, not an error, for a methods paper introducing v-USPhydro with bulk viscosity at freeze-out. Overall: a careful, well-validated simulation study whose central qualitative claim is supported, with a quantitative caveat the authors themselves flag and which the reader's CONDITIONAL verdict already captures. I would keep the verdict as is and, if anything, ask only for tighter abstract wording rather than new physics.","tokens_in":26809,"tokens_out":2187,"duration_ms":36621,"concrete_test":"Re-run the 20–30% centrality class with the temperature-dependent η/s of Eq. (7) and ζ/s set equal to that same η/s (not 0.007), using both the MOM and MH δf^Bulk. Check whether the pion spectrum remains positive over pT = 0–2 GeV for both prescriptions. If it does not, the compensation claim cannot be evaluated at physically relevant viscosities with the present freeze-out treatment, and the abstract's generic statement is supported only by the truncated 10ζ/s and the unphysically small 0.007 cases.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The abstract (abstract:s1) states generically that bulk viscosity reduces the shear-induced suppression of v_n. The size of that reduction at the paper's own default ζ/s from Eq. (9) is small: in Fig. 3 the shear+bulk squares sit only slightly above the shear-only circles, and the authors themselves note that 'our initial bulk viscosity is so small that even after multiplying by a factor of 10, its peak is still not as large as the minimum of the shear viscosity.' The visually striking compensation — v_n pushed close to the ideal curve — appears only in the 10ζ/s diamonds of Fig. 3. But that is exactly the case where the authors report that the viscous correction to the distribution function drives the spectrum negative, forcing them to truncate the pT integration at 0.8 GeV (Section IV A) and to omit the 10ζ/s curve entirely from the differential plots (Section IV B). So the headline effect is demonstrated in a regime where δf is outside its domain of validity. The second demonstration, Section IV C, sets ζ/s = η/s = 0.007, roughly an order of magnitude below the η/s ≈ 0.08–0.2 used everywhere else and below the value the paper itself cites as the near-perfect-fluid benchmark. The regime where the claim would actually matter — ζ/s comparable to a realistic η/s — is precisely the regime the paper does not show, because δf^Bulk breaks down there. This is a sharper version of the reader's δf-model-dependence point: it is not only that MOM and MH disagree, but that the only parameter points where the effect is large are points where neither prescription is trustworthy.","agreement_with_reader":"partial"},"referee_report":{"model":"selfhosted/deepseek-v4.1-flash","summary":"The manuscript uses v-USPhydro, a 2+1 boost-invariant event-by-event SPH hydrodynamics code that includes both shear and bulk viscosity in the equations of motion and in the Cooper-Frye freeze-out, to study how bulk viscosity modifies the shear-induced suppression of the flow harmonics v_n at RHIC (200 A GeV, MC Glauber initial conditions, 150 events per centrality). The central claim, stated in abstract:s1, is that adding bulk viscosity reduces the shear-viscosity-driven suppression of v_n and brings them closer to the ideal-hydrodynamic values. The evidence is twofold: Tables III-V show that bulk viscosity lowers the mean and variance of the shear stress tensor components pi00 and pi12 during the evolution, and Figs. 3-8 show that the viscous-to-ideal ratio of v_n is closer to unity when bulk viscosity is included alongside shear. The authors argue that, depending on the magnitude of zeta/s in the QGP, this may require a re-evaluation of previous shear-only estimates of eta/s.","tokens_in":27161,"tokens_out":5071,"duration_ms":93780,"significance":"If the effect holds at physically relevant values of zeta/s, it would matter: shear-only fits to flow data would systematically bias extracted eta/s, and the interplay between the two viscosities would need to be treated jointly. The code is validated against two independent benchmarks in Appendix A (the TECHQM shear-viscosity test in Fig. 11 and the Gubser SO(3) x SO(1,1) x Z2 semi-analytical Israel-Stewart solution in Fig. 12), which is a genuine strength and gives confidence in the numerical evolution. The dynamical observation that bulk viscosity suppresses the shear stress tensor (Tables III-V) is a robust, delta-f-independent result and is the most convincing part of the paper. The phenomenological reach of the flow-harmonic claim, however, is limited by the delta-f model dependence and by the parameter regimes in which the compensation is demonstrated.","major_comments":[{"comment":"The equation of state used for the production runs is never specified. Eq. (9) defines zeta/s through c_s^2, and the temperature evolution, the freeze-out hypersurface, and the value of c_s^2(T) all depend on the EOS, so the results cannot be reproduced or assessed without it. The only EOS statement in the paper is in Appendix A1 ('We use an ideal equation of state'), which applies to the TECHQM test, not to the RHIC production runs. Please state the EOS used for the main results and the corresponding c_s^2(T), and confirm that the same EOS enters Eq. (9).","section":"Section II B, Eq. (9)","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The 10 zeta/s diamonds in Fig. 3 are integrated over pT = 0-0.8 GeV, while the shear-only circles and shear+bulk squares are integrated over pT = 0-5 GeV. A ratio of v_n computed over different pT windows is not directly comparable, and the apparent approach to the ideal curve in the diamonds may be partly an artifact of the truncated window. Either recompute all three curves over a common pT interval or present the pT-differential ratio so the comparison is like-for-like.","section":"Section IV A, Fig. 3","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The visually striking compensation of shear effects is demonstrated in two regimes that lie outside the physically relevant parameter space: 10 zeta/s, where the authors report that the viscous correction drives the pion spectrum negative and the pT integral must be truncated (Section IV A), and zeta/s = eta/s = 0.007 (Section IV C), roughly an order of magnitude below the eta/s used everywhere else. At the paper's default zeta/s from Eq. (9), the effect in Fig. 3 is small, as the authors themselves note. The abstract states the claim generically. Please qualify abstract:s1 to state the regime in which the compensation is quantitatively established, or provide a case at a realistic zeta/s with a controlled delta-f.","section":"Section IV A, Section IV C, abstract:s1","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"No uncertainties are shown on any of the flow-harmonic figures despite 150 event-by-event simulations per centrality. For the default zeta/s the shear+bulk and shear-only curves in Fig. 3 differ by only a few percent, and the reader cannot judge whether that difference is statistically significant or comparable to the systematic spread between the MOM and MH delta-f prescriptions. Please add statistical error bands (and, where possible, an estimate of the delta-f systematic) to Figs. 3-8.","section":"Figs. 3-8","authors_acknowledge":null,"authors_acknowledge_p":null}],"minor_comments":[{"comment":"The energy-momentum tensor is written as 'T^{mu nu} = epsilon u^nu u^nu - ...'; the first two factors should presumably be u^mu u^nu. Please correct the index structure.","section":"Eq. (4)","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The initial energy density is normalized so that the average yield is 123 direct pi+ in central collisions, a number the authors describe as the value that, when added to the decay yield, reproduces the measured pi+ count. Since decays are not simulated in this work, please clarify how this normalization is consistent with the absence of a decay contribution and whether it biases the absolute yields.","section":"Section II C","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The bulk relaxation time tau_Pi = 9 zeta/(epsilon - 3p) diverges as epsilon -> 3p. The authors state that they enforce tau_Pi > 0.1 fm, but it would help to state explicitly how the regulator is applied and whether the near-conformal region is ever reached in the evolution.","section":"Eq. (10)","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The Introduction cites [28] for the statement that bulk viscosity enhances the differential flow harmonics with respect to the ideal case, whereas Figs. 5-8 here show the viscous curves lying below the ideal curve. Please reconcile these statements, and clarify in Fig. 10 whether the zeta/s = eta/s = 0.007 curve exceeds the ideal curve or only the small-shear curve.","section":"Introduction vs. Figs. 5-8","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The sign convention for the percentage changes is not stated. Please specify whether a positive entry denotes an increase or a decrease relative to the reference case, so the tables can be read without inference.","section":"Tables II-V","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"There are typographical errors in the reference list, e.g. 'U. WHeinz' in Ref. [22] and inconsistent spacing in 'F AIR'. Please correct these.","section":"References","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The closing sentence that the effect 'may require a re-evaluation of the previous estimates of eta/s' is stronger than the evidence supports, given that no comparison to data is made, only direct pions are considered, and no hadronic afterburner is included. Consider tempering this to a statement about the direction of a possible bias rather than a required re-evaluation.","section":"Abstract","authors_acknowledge":null,"authors_acknowledge_p":null}],"recommendation":"major_revision"},"author_rebuttal":null,"desk_editor":{"model":"selfhosted/deepseek-v4.1-flash","letter":"Bottom line: the part of this worth your time is the dynamical observation, not the headline. Tables III–V show that turning on bulk viscosity suppresses the mean and variance of pi00 through the evolution, and that the effect grows the longer the system expands. That is a clean, model-independent statement about the fluid, and it is the piece I would cite. The abstract's claim that bulk viscosity pushes v_n back toward ideal is true but only demonstrated where the freeze-out prescription is least trustworthy, and the authors mostly know it. Start with the tables, not Fig. 3. What the paper does well: the code is validated against two external benchmarks, the TECHQM shear test and the Gubser semi-analytical Israel-Stewart solution, in Appendix A. That is real and not universal in this literature. The event-by-event setup is standard and the bookkeeping in Tables II–V is careful. Where it is soft: at the paper's own default zeta/s from Eq. (9), the shear+bulk squares in Fig. 3 sit barely above the shear-only circles, and the authors say so. The visually striking recovery toward ideal appears at 10 zeta/s, which is exactly the case where they report the pion spectrum going negative and truncate the pT integral at 0.8 GeV, and where they drop the curve from the differential plots entirely. The second demonstration, Section IV C, uses zeta/s = eta/s = 0.007, an order of magnitude below the eta/s the rest of the paper uses. So the regime where the claim would matter is the regime where delta-f-Bulk is outside its domain. That is a sharper version of the MOM-versus-MH disagreement the paper already flags: the two prescriptions differ qualitatively for v2(pT), and neither is validated where the effect is large. The authors state both limitations in the conclusions, which is to their credit, but the abstract does not carry the qualification. Minor: pions only, no decays, no data comparison, all acknowledged. This deserves a serious referee. The dynamical suppression result stands on its own and the code validation is genuine; the flow-harmonic claim needs to be narrowed to what the parameter space supports.","headline":"The durable result is that bulk viscosity suppresses the shear stress tensor during the evolution; the abstract's flow-harmonic claim is larger than the parameter space actually supports.","tokens_in":27803,"tokens_out":1170,"duration_ms":20346},"pith_extraction":{"msc":[],"pacs":["25.75.-q","25.75.Ld","47.75.+f","12.38.Mh"],"model":"selfhosted/deepseek-v4.1-flash","headline":"Bulk viscosity partly cancels shear viscosity's damping of flow harmonics in heavy-ion collisions, the paper argues, so earlier fits of $η/s$ may need revisiting.","keywords":["quark-gluon plasma","bulk viscosity","shear viscosity","flow harmonics","relativistic hydrodynamics","event-by-event simulations","heavy-ion collisions","Cooper-Frye freeze-out"],"falsifier":"A first-principles kinetic-theory derivation of the bulk viscous correction to the freeze-out distribution, replacing the two competing prescriptions the paper compares, that leaves the differential $v_n(p_T)$ unchanged or further suppressed when bulk viscosity is added to shear would undercut the claim; so would a hydrodynamic run that includes the direct $Π$–$π^{μν}$ coupling terms and finds no reduction of $⟨π^{00}⟩$ when bulk viscosity is switched on.","tokens_in":28152,"feed_emoji":"🌀","tokens_out":2670,"duration_ms":45884,"temperature":0.7,"pith_summary":"Heavy-ion collisions at RHIC produce a droplet of quark-gluon plasma whose azimuthal flow harmonics $v_n$ are the standard handle on how fluid-like the medium is. Shear viscosity is known to damp those harmonics below their ideal-fluid values, and that damping is what previous work used to pin down $η/s$. This paper asks what happens when bulk viscosity is switched on at the same time, using an event-by-event 2+1 relativistic hydrodynamic code that carries both viscosities through the evolution and through freeze-out. The answer the authors argue for is that bulk viscosity softens shear's damping, pushing the harmonics back toward ideal-hydro values, and that the effect is visible both in the evolution of the shear stress tensor and in the final $v_n$. If that is right, fits that ignored bulk viscosity would have compensated by choosing too small an $η/s$.","feed_headline":"Bulk viscosity cancels part of shear's damping of flow","feed_subtitle":"Adding bulk viscosity pushes flow harmonics back toward ideal values, which could unsettle extracted shear viscosity.","key_machinery":"The vehicle is v-USPhydro, a boost-invariant 2+1 Lagrangian code that solves the Israel-Stewart equations for $Π$ and $π^{μν}$ with smoothed-particle hydrodynamics on Monte Carlo Glauber initial conditions, and then applies viscous corrections to the Cooper-Frye freeze-out distribution. The load-bearing mechanism is the indirect coupling between the two dissipative sectors through the fluid velocity: bulk viscosity resists radial expansion, which in turn reduces the diagonal components of the shear stress tensor, which in turn lessens the shear-driven dilution of $v_n$. The paper quantifies this with percentage changes in the mean and variance of $Π$, $π^{00}$, and $π^{12}$ across centrality classes and across early, late, and full freeze-out slices, and then translates it into ratios of viscous to ideal $v_n$.","core_discovery":"The paper's central claim is that bulk and shear viscosity do not act independently on the flow harmonics: adding bulk viscosity reduces the shear-viscosity-induced suppression of $v_n$ and brings the harmonics closer to their ideal-hydrodynamic values. The authors support this in two ways. First, in the hydrodynamic evolution itself, they show that switching on bulk viscosity lowers the mean value of the $π^{00}$ component of the shear stress tensor (by roughly 18 to 45 percent depending on centrality, and by less at early times) and shrinks its event-by-event variance by around 20 percent, while $π^{12}$ is only mildly affected. Second, in the final spectra, the viscous-to-ideal ratio of the integrated $v_n$ sits closer to unity for shear-plus-bulk than for shear alone, and the same ordering appears in the differential $v_2(p_T)$ through $v_5(p_T)$. The authors emphasize that the coupling is indirect: $Π$ and $π^{μν}$ do not appear in each other's equations of motion in their setup, so the effect runs through the bulk-viscosity-modified flow velocity, and it grows the longer the system expands. They also show a case with $ζ/s = η/s = 0.007$, where the integrated harmonics return almost exactly to the ideal values, with $v_5$ the exception.","pith_inferences":["If bulk viscosity can mimic a smaller shear viscosity in the integrated $v_n$, then a joint $η/s$–$ζ/s$ extraction from the same data should show a valley of acceptable fits rather than a point, and the shape of that valley is itself a testable prediction.","The authors' observation that the effect strengthens at late times suggests a cheap diagnostic: comparing flow harmonics on freeze-out slices at different temperatures would reveal whether the compensation is dynamical or merely a freeze-out bookkeeping artifact.","Because the coupling here is indirect, the size of the effect is a direct measure of how much the bulk pressure distorts the velocity field; a calculation with the direct $Π$–$π^{μν}$ coupling terms switched on would tell us whether the effect found here is a floor or a ceiling.","The claim also implies that the commonly quoted near-perfect-fluid value of $η/s$ is not by itself evidence about the plasma, since a larger $η/s$ paired with a non-negligible $ζ/s$ could reproduce the same spectra."],"forward_implications":["Extractions of $η/s$ from hydrodynamic fits to RHIC flow data that omitted bulk viscosity would be biased low, since bulk viscosity supplies part of the flow that was attributed to a smaller shear viscosity.","The bias should grow with system lifetime, so the same effect should be stronger at LHC energies and at lower freeze-out temperatures, where the fluid spends longer in the plasma phase.","Higher-order harmonics are the least able to be fully restored by bulk viscosity, so $v_4$ and $v_5$ are the more discriminating observables for separating the two transport coefficients.","In central collisions a large $ζ/s$ compresses the gap between $v_2$ and $v_3$, which is a qualitative shape change in the harmonic spectrum rather than a uniform rescaling."],"supporting_citations":[{"why":"The authors' earlier v-USPhydro study of bulk viscosity alone at RHIC, which supplies the code, the bulk-only baseline, and the moments-method freeze-out correction this paper extends to shear-plus-bulk.","marker":"[28]"},{"why":"Source of the moments-method derivation of the bulk viscous correction to the distribution function and of the general Israel-Stewart equations the code implements.","marker":"[32]"},{"why":"The Monnai-Hirano Grad 14-moment prescription for the bulk viscous $δf$, the second freeze-out model against which the differential-flow results are compared.","marker":"[24]"},{"why":"Supplies the temperature-dependent $η/s$ parametrization, joining hadronic-model results at low $T$ to lattice data at high $T$, used in all production runs.","marker":"[39]"},{"why":"Provides the Buchel-form $ζ/s = (1/8π)(1/3 - c_s^2)$ used as the baseline bulk viscosity throughout the paper.","marker":"[42]"},{"why":"Semi-analytical Israel-Stewart solutions with transverse dynamics used to validate the shear sector of v-USPhydro before production runs.","marker":"[35]"},{"why":"The TECHQM code-checking benchmark against which the ideal and shear-viscous evolution of the code is verified.","marker":"[52]"}],"fun_headline_variants":["Bulk viscosity blunts shear's damping of RHIC flow harmonics","Adding bulk viscosity pulls flow harmonics back toward ideal values","Bulk viscosity indirectly weakens shear's effect on flow harmonics","Bulk and shear viscosity interact in RHIC flow harmonics","Bulk viscosity may shift extracted shear viscosity of quark-gluon plasma"],"cache_read_input_tokens":0,"weakest_assumption_plain":"The differential-flow half of the claim rests on how the bulk viscous correction to the freeze-out particle distribution is modeled: the paper's own two prescriptions, Monnai-Hirano and the moments method, give visibly different $v_2(p_T)$, with one nearly reproducing the ideal curve and the other suppressing it, so the claim holds only if at least one of them is close to the true correction.","fun_headline_variants_meta":{"raw":{"variants":["Bulk viscosity blunts shear's damping of RHIC flow harmonics","Adding bulk viscosity pulls flow harmonics back toward ideal values","Bulk viscosity indirectly weakens shear's effect on flow harmonics","Bulk and shear viscosity interact in RHIC flow harmonics","Bulk viscosity may shift extracted shear viscosity of quark-gluon plasma"]},"model":"selfhosted/deepseek-v4.1-flash","effort":"low","attempts":1,"cost_usd":0.0,"raw_usage":{"total_tokens":2707,"prompt_tokens":972,"completion_tokens":1735,"prompt_tokens_details":null,"completion_tokens_details":{"reasoning_tokens":1662}},"tokens_in":972,"tokens_out":1735,"duration_ms":31119,"image_pages":[],"temperature":1.0,"reasoning_budget":50,"reasoning_tokens":1662,"transport_provider":"selfhosted","cache_read_input_tokens":0,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-10-29T05:41:00.258039+00:00","model_set":{"reader":"selfhosted/deepseek-v4.1-flash"},"pipeline_version":"pith-pipeline@v1.5.0-archive-selfhost","input_kind":null,"input_chars":null,"input_total_chars":null,"passes_missing":null,"published_standing":null,"published_confidence":null,"objection_audit":null,"run_record":null,"basis":{"kind":"not_recorded","source":null,"chars_given":null,"chars_total":null},"receipt":null,"falsifier":"A first-principles kinetic-theory derivation of the bulk viscous correction to the freeze-out distribution, replacing the two competing prescriptions the paper compares, that leaves the differential $v_n(p_T)$ unchanged or further suppressed when bulk viscosity is added to shear would undercut the claim; so would a hydrodynamic run that includes the direct $Π$–$π^{μν}$ coupling terms and finds no reduction of $⟨π^{00}⟩$ when bulk viscosity is switched on.","supporting_citations":[{"cited_title":"Bulk viscosity, particle spectra and flow in heavy-ion collisions","cited_arxiv_id":"1109.5181","evidence_quote":"The authors' earlier v-USPhydro study of bulk viscosity alone at RHIC, which supplies the code, the bulk-only baseline, and the moments-method freeze-out correction this paper extends to shear-plus-bulk."},{"cited_title":"J. Phys. G 27, 75","cited_arxiv_id":null,"evidence_quote":"Source of the moments-method derivation of the bulk viscous correction to the distribution function and of the general Israel-Stewart equations the code implements."},{"cited_title":"Bulk and shear viscosities of matter created in relativistic heavy-ion collisions","cited_arxiv_id":"0911.2397","evidence_quote":"The Monnai-Hirano Grad 14-moment prescription for the bulk viscous $δf$, the second freeze-out model against which the differential-flow results are compared."},{"cited_title":"A Study of the Di-Hadron Angular Correlation Function in Event by Event Ideal Hydrodynamics","cited_arxiv_id":"1305.3098","evidence_quote":"Supplies the temperature-dependent $η/s$ parametrization, joining hadronic-model results at low $T$ to lattice data at high $T$, used in all production runs."},{"cited_title":"Origin of the Relaxation Time in Dissipative Fluid Dynamics","cited_arxiv_id":"1102.4780","evidence_quote":"Provides the Buchel-form $ζ/s = (1/8π)(1/3 - c_s^2)$ used as the baseline bulk viscosity throughout the paper."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Semi-analytical Israel-Stewart solutions with transverse dynamics used to validate the shear sector of v-USPhydro before production runs."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The TECHQM code-checking benchmark against which the ideal and shear-viscous evolution of the code is verified."}],"lane_accuracy":{"status":"not yet measured","lane":{"model":"selfhosted/deepseek-v4.1-flash","input_kind":null},"url":"https://pith.science/accuracy"},"review_version":1}