{"id":"68c4406f-866b-4e90-9951-968b39a4672b","arxiv_id":"2605.03093","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":6.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Remnant magnetic fields induce collective rotation in QCD matter via the Einstein-de Haas effect at levels comparable to typical fluid vorticity in heavy-ion collisions.","lead":"The paper reports the first identification of the Einstein-de Haas effect in hot QCD matter, where an external magnetic field aligns particle spins in an equilibrium hadron gas and induces collective rotation to conserve angular momentum. This rotation from remnant fields at freeze-out is claimed to reach magnitudes comparable to fluid vorticity inferred from hyperon polarization in heavy-ion collisions, without needing initial vorticity as input.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.3","headline":"Equilibrium hadron gas model assumes static uniform B and direct AM transfer from spin alignment to collective rotation, but HIC freeze-out is dynamical and inhomogeneous.","rationale":"The reader's weakest assumption directly identifies the modeling step that must hold for the numerical comparability claim to be valid. Because the full text was not supplied in the query, no independent derivation or numerical check could be performed, so the unverdicted status is retained.","tokens_in":1663,"tokens_out":368,"duration_ms":25850,"concrete_test":"Take the paper's equilibrium distribution for protons and Λ at T=155 MeV, B=0.05 GeV² (typical remnant value), compute total spin AM per unit volume, then impose rigid rotation ω on the momentum distribution and check whether the resulting orbital AM exactly cancels it while preserving the observed p_T spectra; if the required ω differs by more than a factor of two from the quoted 0.01–0.05 fm⁻¹ range, the compensation mechanism fails.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim requires that remnant B at freeze-out induces net spin polarization whose total angular momentum is exactly compensated by a macroscopic rigid-body rotation ω_EdH of the entire system, with no initial vorticity. This rests on treating the hadron gas as globally equilibrated in a constant external field, so that the Boltzmann factor exp(μ·B/T) produces a calculable <S_z> per species whose sum equals Iω. In the actual collision, freeze-out occurs in a rapidly expanding, inhomogeneous, time-dependent remnant field; particles decouple and free-stream, so local spin alignment does not automatically generate a global orbital velocity field. No section demonstrates how the required momentum redistribution occurs without additional interactions or initial conditions.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript claims to report the first identification of the Einstein-de Haas effect in QCD matter. Using an equilibrium hadron gas model under an external magnetic field, it shows that even remnant magnetic fields at freeze-out produce induced rotations (ω_EdH) comparable to typical estimates of fluid vorticity in heavy-ion collisions as inferred from final-state hyperon polarization. This rotation is generated from the magnetic field alone, without any initial vorticity input, establishing hot QCD matter as a self-vortical magnetofluid where spin-rotation coupling is an important component of angular momentum dynamics.","tokens_in":1831,"tokens_out":499,"duration_ms":46809,"significance":"If the central result holds, the work identifies a magnetomechanical coupling that could contribute to collective rotation in relativistic nuclear collisions purely via spin alignment, potentially affecting the interpretation of polarization observables and angular momentum balance in the presence of strong magnetic fields. The equilibrium model yields a concrete, parameter-free prediction for the induced ω_EdH that can be compared directly to existing vorticity estimates.","major_comments":[{"comment":"Abstract and model description: the claim that remnant B fields at freeze-out induce ω_EdH comparable to fluid vorticity without initial vorticity input rests on treating the hadron gas as globally equilibrated in a static, uniform external magnetic field, so that the Boltzmann factor produces a net <S_z> per species whose total angular momentum is exactly compensated by a macroscopic rigid-body rotation Iω_EdH. In heavy-ion collisions, freeze-out occurs in a rapidly expanding, inhomogeneous, time-dependent remnant field with particles decoupling and free-streaming; no section demonstrates how local spin alignment generates the required global orbital velocity field without additional interactions or initial conditions.","section":"Abstract and model description"}],"minor_comments":[{"comment":"The abstract would be strengthened by including at least one key equation (e.g., the expression for ω_EdH or the sum over species for total spin angular momentum) and a numerical value or ratio showing the claimed comparability to vorticity.","section":"Abstract"},{"comment":"Notation for ω_EdH and the moment of inertia should be defined explicitly on first use to improve readability for readers outside the immediate subfield.","section":null}],"recommendation":"major_revision","confidential_remarks":"The manuscript is submitted to a hep-ph arXiv but its content sits at the boundary between high-energy nuclear theory and magnetohydrodynamics; the editor may wish to confirm scope fit with the journal."},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the careful reading and constructive feedback on our manuscript. We address the major comment below.","responses":[{"response":"We agree that the calculation employs an equilibrium hadron gas in a static, uniform magnetic field. This framework permits a direct evaluation of the field-induced net spin per species through the Boltzmann factor and the compensating rigid-body rotation Iω_EdH required by angular-momentum conservation. The resulting parameter-free estimate shows that remnant fields at freeze-out can produce ω_EdH values comparable to typical fluid vorticity. The model is intended as an order-of-magnitude illustration of the Einstein-de Haas effect under freeze-out conditions rather than a full dynamical simulation of the expanding medium. A complete demonstration of how local spin alignments source a global velocity field would indeed require a non-equilibrium treatment (e.g., spin hydrodynamics or kinetic theory with spin-rotation coupling), which lies outside the present scope. We will revise the abstract and model-description sections to state the equilibrium assumptions and limitations more explicitly and will add a short discussion paragraph outlining how the effect could be incorporated into future dynamical models.","revision_made":"partial","referee_comment":"[Abstract and model description] Abstract and model description: the claim that remnant B fields at freeze-out induce ω_EdH comparable to fluid vorticity without initial vorticity input rests on treating the hadron gas as globally equilibrated in a static, uniform external magnetic field, so that the Boltzmann factor produces a net <S_z> per species whose total angular momentum is exactly compensated by a macroscopic rigid-body rotation Iω_EdH. In heavy-ion collisions, freeze-out occurs in a rapidly expanding, inhomogeneous, time-dependent remnant field with particles decoupling and free-streaming; no section demonstrates how local spin alignment generates the required global orbital velocity field without additional interactions or initial conditions."}],"tokens_in":1300,"tokens_out":390,"duration_ms":69150,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main takeaway is that this work identifies the Einstein-de Haas effect in QCD matter by treating an equilibrium hadron gas under an external magnetic field. It calculates that even weak remnant fields at freeze-out generate a compensating collective rotation whose magnitude matches the vorticity inferred from hyperon polarization data, and that this rotation appears without any initial vorticity input.","headline":"The paper applies the Einstein-de Haas effect to an equilibrium hadron gas and finds remnant magnetic fields can induce rotations comparable to typical vorticity estimates, but the static uniform-field assumption clashes with the dynamical freeze-out in heavy-ion collisions.","tokens_in":2343,"tokens_out":156,"would_cite":false,"duration_ms":20904,"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":"Remnant magnetic fields at freeze-out induce rotations in QCD matter comparable to fluid vorticity via the Einstein-de Haas effect.","keywords":["Einstein-de Haas effect","QCD matter","heavy-ion collisions","magnetic fields","vorticity","spin alignment","angular momentum"],"falsifier":"A calculation or measurement demonstrating that the induced rotation from remnant magnetic fields is much smaller than the vorticity values inferred from hyperon polarization would falsify the comparability.","tokens_in":2546,"feed_emoji":"🧲","tokens_out":591,"duration_ms":26485,"temperature":0.7,"pith_summary":"This paper reports the first identification of the Einstein-de Haas effect in QCD matter. The effect arises when magnetic-field-induced spin alignment in an equilibrium hadron gas generates a compensating collective rotation to conserve total angular momentum. Calculations demonstrate that even remnant magnetic fields produce induced rotations similar in magnitude to typical fluid vorticity estimates from hyperon polarization in heavy-ion collisions. This occurs without any initial vorticity input, establishing hot QCD matter as a self-vortical magnetofluid where spin-rotation coupling plays a key role in angular momentum dynamics.","feed_headline":"Magnetic fields induce rotations in hot QCD matter","feed_subtitle":"Even remnant fields at freeze-out generate effects comparable to fluid vorticity from hyperon polarization data.","key_machinery":"The Einstein-de Haas effect, defined as the magnetomechanical coupling in which spin alignment under a magnetic field produces a compensating collective rotation to conserve total angular momentum.","core_discovery":"The central claim is that the Einstein-de Haas effect can be realized in an equilibrium hadron gas under external magnetic fields, leading to induced rotations ω_EdH that match typical values of fluid vorticity in relativistic nuclear collisions, all emerging purely from the magnetic field and spin alignment.","pith_inferences":["This mechanism could provide an alternative or additional source for observed hyperon polarizations in heavy-ion data.","Models of angular momentum in collisions may need to account for magnetic field contributions to rotation separately from hydrodynamic vorticity.","Further studies could explore how this effect influences other spin observables or the evolution of magnetic fields in the plasma."],"forward_implications":["Collective rotation can be generated in QCD matter purely from magnetic spin alignment without initial fluid vorticity.","Spin-rotation coupling becomes an important, previously overlooked component of angular momentum dynamics in heavy-ion collisions.","Hot QCD matter behaves as a self-vortical magnetofluid due to this effect.","The induced rotations are comparable to those inferred from final-state hyperon polarization."],"fun_headline_variants":["EdH effect rotates QCD matter","Magnetic fields induce EdH rotation in QCD","Spin alignment generates rotation in QCD matter","Remnant fields cause EdH rotation at freeze-out"],"cache_read_input_tokens":64,"weakest_assumption_plain":"The system can be treated as an equilibrium hadron gas under an external magnetic field where spin alignment directly produces a compensating collective rotation while conserving total angular momentum.","fun_headline_variants_meta":{"raw":{"variants":["EdH effect rotates QCD matter","Magnetic fields induce EdH rotation in QCD","Spin alignment generates rotation in QCD matter","Remnant fields cause EdH rotation at freeze-out"]},"model":"grok-4.3","cost_usd":0.004643,"raw_usage":{"total_tokens":2168,"prompt_tokens":568,"num_sources_used":0,"completion_tokens":52,"cost_in_usd_ticks":46428000,"prompt_tokens_details":{"text_tokens":568,"audio_tokens":0,"image_tokens":0,"cached_tokens":64},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1548,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":568,"tokens_out":52,"duration_ms":25955,"temperature":1.0,"reasoning_tokens":1548,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-08T17:30:06.665185+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A calculation or measurement demonstrating that the induced rotation from remnant magnetic fields is much smaller than the vorticity values inferred from hyperon polarization would falsify the comparability.","supporting_citations":[],"review_version":1}