{"id":"243c66fe-0e24-4644-afbb-863b29291f25","arxiv_id":"2607.05333","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":7,"one_line_summary":"Mass-gap compact objects (2.5–5 M☉) can be modeled as neutron stars within f(R,T)=R+2λT gravity using the AV18 equation of state with Bowers-Liang anisotropy and strong magnetic fields.","lead":"This paper uses a modified gravity theory (f(R,T) gravity) with a realistic nuclear equation of state to model neutron stars, showing that objects in the 2.5–5 solar mass 'mass gap' could be neutron stars rather than black holes. A generalist might read it because it offers a theoretical explanation for mysterious compact objects detected by gravitational-wave observatories.","discovery_kind":"unclear","skeptic_critique":{"model":"glm-5.2","headline":"The coupling constant λ is treated as a per-object free parameter spanning three orders of magnitude (−0.001 to −3), undermining the claim of a unified gravitational explanation for mass-gap objects.","rationale":"The reader correctly identified the per-object parameter fitting as the most load-bearing concern. I agree and would sharpen it further: the issue is not merely that different parameter combinations are used per object, but that λ — a fundamental coupling constant of the gravitational theory — varies by three orders of magnitude across objects (from −0.001 for PSR J0740+6620 to −3 for GW190814). This is not statistical underfitting; it is treating a law-of-nature constant as a tunable per-object parameter. No single λ value can simultaneously match a well-constrained NICER source and a mass-gap object, as a quick check of Table II confirms: at λ = −2 the minimum mass already exceeds PSR J0740+6620's mass with a radius far below its observed value, while at λ = −0.001 the maximum mass cannot reach the mass gap. The paper's derivation of the modified TOV equations (Eqs. 37–38) appears internally consistent, the EoS satisfies causality (Fig. 3), and the framework does reach the required masses. These are real strengths. However, the claim that mass-gap objects 'can be interpreted as neutron stars' is overstated: the paper demonstrates that the framework's parameter space contains configurations matching each observed mass individually, not that a single theory with fixed parameters explains them collectively. The paper itself acknowledges model dependence in Sec. VI but does not confront the λ-variation issue specifically. I also note a secondary concern: no stability analysis is provided for the high-mass configurations (up to 3.3 M☉), which would be needed to confirm these are stable equilibrium solutions rather than unstable branch points. The verdict of CONDITIONAL is appropriate: the mathematical framework is sound, but the physical claim requires either a single unified parameter fit or explicit reframing as a parameter-space exploration. The reader's assessment is accurate and I see no reason to adjust the verdict.","tokens_in":25071,"tokens_out":4857,"duration_ms":102650,"concrete_test":"Attempt a simultaneous fit: fix a single λ value and search over (β, B_surf, central density) to reproduce both PSR J0740+6620 (M = 2.08 M☉, R = 13.7 km) and GW190814 (M = 2.59 M☉) within their observational uncertainties. Specifically, scan λ from −3 to 0 in steps of 0.1; for each λ, compute the M–R curve for β ∈ [0, 1] and check whether any single (λ, β) pair yields a curve passing through both the PSR J0740+6620 error box and the GW190814 mass band. If no single λ works, the framework cannot provide a unified explanation and the claim should be reframed as a parameter-space existence proof, not an interpretation of specific objects.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is that mass-gap objects (GW190814 at 2.59 M☉, GW200210 at 2.83 M☉) can be interpreted as neutron stars within f(R,T) = R + 2λT gravity. For this to constitute a physical explanation rather than a flexible parameterization, λ must be a single fundamental coupling constant of the gravitational theory, applicable to all objects. Yet Table VII assigns vastly different values: PSR J0740+6620 uses λ = −0.001 (essentially GR), while GW190814 uses λ = −3 and GW200210 uses λ = −2. This is not merely statistical underfitting — it is using different effective laws of gravity for different objects. The paper itself frames the range λ ∈ [−3, −0.1] as covering all observations (text around Fig. 6), but does not address that no single λ value within this range can simultaneously reproduce a well-constrained NICER source like PSR J0740+6620 (2.08 M☉, R = 13.7 km) and a mass-gap object like GW190814 (2.59 M☉). For instance, at λ = −2 with B_surf = 10^17 G (Table II), the minimum mass at β = 0 is already 2.098 M☉ with R ≈ 9.56 km — far below the observed radius of PSR J0740+6620. Conversely, λ = −0.001 cannot reach 2.59 M☉ even with maximal anisotropy (Table II gives 2.565 M☉ at β = 1.0 only for B_surf = 5×10^16 G, and the radius would be ~9.5 km, inconsistent with any mass-gap object constraint). The paper acknowledges model dependence in Sec. VI but does not confront the inconsistency of varying a fundamental constant per object. Additionally, the paper provides no stability analysis (radial perturbation eigenmodes) for configurations reaching 3.3 M☉, which is essential for claiming these are physical neutron stars rather than unstable branch solutions.","agreement_with_reader":"agree"},"referee_report":{"model":"glm-5.2","summary":"This paper studies neutron star structure in the f(R,T) = R + 2λT model of modified gravity, using the AV18 nucleon-nucleon potential to construct the equation of state (EoS). The authors derive modified isotropic and anisotropic TOV equations (the latter incorporating the Bowers-Liang anisotropy prescription and a density-dependent Gaussian magnetic field profile), solve them numerically, and compute structural quantities including maximum mass, radius, Schwarzschild radius, compactness, surface redshift, and the Kretschmann scalar. The central claim is that mass-gap objects (2.5–5 M☉), specifically the secondary components of GW190814 (2.59 M☉) and GW200210-092254 (2.83 M☉), can be interpreted as neutron stars rather than black holes within this framework. The authors present a table (Table VII) in which the parameters (λ, β, B_surf) are selected to reproduce the observed masses and radii of 17 compact objects.","tokens_in":25607,"tokens_out":2119,"duration_ms":164306,"significance":"The question of whether mass-gap compact objects are neutron stars or black holes is of substantial astrophysical interest, and the systematic derivation of the anisotropic modified TOV equations in f(R,T) gravity (Eqs. 37–38) is a useful technical contribution. The use of a microscopic EoS (AV18 via the LOCV method) and the verification of causality (Fig. 3) are commendable. The computation of the Kretschmann scalar and the demonstration that R_Sch < R for all models provide a self-consistency check that the configurations are not black holes. However, the significance of the central claim is substantially undermined by the treatment of λ as a per-object free parameter (see major comments).","major_comments":[{"comment":"Table VII and surrounding text (Sec. V): The central claim that mass-gap objects 'can be interpreted as neutron stars' is achieved by assigning a different λ value to each object — e.g., λ = −0.001 for PSR J0740+6620, λ = −3 for GW190814, λ = −2 for GW200210-092254. In f(R,T) = R + 2λT gravity, λ is a fundamental coupling constant of the gravitational theory, not a property of individual stars. Using different effective laws of gravity for different objects does not constitute a unified physical explanation. The paper does not address this issue; the acknowledgment in Sec. VI that results are 'model-dependent' refers to the choice of EoS and anisotropy prescription, not to the per-object variation of a fundamental constant. This is the load-bearing concern for the paper's central claim.","section":null},{"comment":"Sec. III.A, text around Fig. 6 (p. 7): The paper states that the parameters are set 'such that the model simultaneously traverses the constraints from mass and radius of the component of GW170817, and masses of the components of GW190814 and GW200210-092254, as well as satisfies the constraints from masses and radii of PSR J0740+6620 and PSR J0030+0451.' This claim of simultaneous satisfaction is contradicted by Table VII, where no single (λ, β) pair reproduces more than one or two objects. The text should be revised to accurately describe what the table shows: individual a posteriori fitting, not simultaneous constraint satisfaction.","section":null},{"comment":"Table VII, PSR J0740+6620 row: The observed radius is 13.7^{+2.6}_{−1.5} km, but the theoretical radius reported is 8.714 km (for B_surf = 5.0×10^16 G) or 8.415 km (for B_surf = 1.0×10^17 G, listed for PSR J0348+0432 with the same λ, β). These radii are more than 5σ below the NICER constraint. The paper does not discuss this discrepancy. If the model cannot reproduce the radius of a well-constrained NICER source at the λ value used for that source, the claim of consistency with observational data is overstated.","section":null},{"comment":"Sec. IV, Eq. (39): The Schwarzschild radius in f(R,T) gravity is given as R_Sch = (2GM/c²)(1 + 3λ/8π). For λ = −3, the correction factor is 1 − 9/(8π) ≈ 0.642, a 36% reduction. For λ approaching −8π/3, R_Sch vanishes. The paper uses R_Sch < R as evidence that the objects are not black holes, but this criterion is modified by the f(R,T) correction itself. The paper should discuss whether this modified R_Sch criterion is the appropriate horizon condition in f(R,T) gravity, or whether the standard GR Schwarzschild radius (2GM/c²) should be used for the black-hole comparison.","section":null}],"minor_comments":[{"comment":"Abstract: 'We show that some compact objects residing in the mass gap interpreted as candidates of neutron stars' is grammatically incomplete; a verb is missing.","section":null},{"comment":"Sec. III.B, Eq. (30) line: 'where u^μ defined benight Eq. (27)' — 'benight' appears to be a typo, likely 'by'.","section":null},{"comment":"Sec. III.A, p. 7: 'the linear madel of f(R, T) gravity' — 'madel' should be 'model'.","section":null},{"comment":"Table III caption: 'Schwarzchild' should be 'Schwarzschild' (also appears in the text on p. 12).","section":null},{"comment":"Sec. VI: The stray text '0.00,0.07,1.00Collectively, inf(R, T) gravity' appears to be a formatting artifact and should be removed.","section":null},{"comment":"Table VII: The B_surf entry for PSR J0952-0607 (first row) is listed as '−1.0×10^17 G', which is presumably a typo for '1.0×10^17 G'.","section":null},{"comment":"Table VII: The B_surf entries for GW190814 and GW200210-092254 are listed as '−1.0×10^17 G', which should be '1.0×10^17 G'.","section":null},{"comment":"Sec. II, Eq. (10): The parameters η and θ are introduced but their values are only specified in the text (η = 0.05, θ = 2.0 for the adopted slow-decay configuration). It would help to state these values in the caption of Fig. 2 or in a table for clarity.","section":null},{"comment":"Sec. III.A, Eq. (29): The definition ζ ≡ 8π + 2λ is dimensionally inconsistent if λ is dimensionless and 8π is dimensionless in geometric units. The paper should clarify the units or conventions used.","section":null},{"comment":"Fig. 5 and Fig. 8: The observational error regions for several objects (e.g., GW190814, GW200210) are shown without radius constraints. It would be helpful to explicitly state in the figure caption that these objects have mass-only constraints.","section":null},{"comment":"Sec. IV, Eq. (43): The Kretschmann scalar expression contains a factor of λ in the second term and λ² in the third, but the first term has no explicit λ dependence. The derivation or reference for this expression should be provided.","section":null},{"comment":"Table I: The entry for λ = −10^{−7} gives M_max = 1.750 M☉, which is lower than the λ = −0.001 entry (2.197 M☉) despite being closer to zero. The monotonicity of the mass–λ relation should be verified or the non-monotonicity explained.","section":null},{"comment":"Sec. V, p. 14: The text states 'to reproduce the results of an event like the mass of GW230529A: (i) For B_surf = 5.0×10^16 G, the free parameters λ and β must take the values −2.0 and 1.0. (ii) Conversely, for B_surf = 1.0×10^17 G, the values must be −3.0 and 1.0.' However, Table VII lists GW230529A with λ = −3, β = 1.0, B_surf = 5.0×10^16 G. This inconsistency should be corrected.","section":null}],"recommendation":"major_revision","confidential_remarks":"The core issue is that the paper's central claim rests on treating a fundamental coupling constant as a per-object fitting parameter. This is a conceptual problem, not merely a presentation issue. The authors could potentially salvage the paper by either (a) reframing the claim as a parameter-space exploration showing what λ values would be required for each object, without claiming a unified explanation, or (b) attempting a joint fit with a single λ value and honestly reporting which objects can and cannot be reproduced. Option (a) is more feasible within the scope of revision. The radius discrepancy for PSR J0740+6620 (8.7 km vs. 13.7 km observed) is also a serious concern that the authors do not address at all."},"author_rebuttal":{"model":"glm-5.2","summary":"We thank the referee for a careful and substantive report. The major comments identify genuine issues that require revision of the manuscript's framing and claims. We address each below.","responses":[{"response":"The referee is correct that in f(R,T) = R + 2λT gravity, λ is a fundamental coupling constant of the theory, not a property of individual stars. We acknowledge that assigning different λ values to different objects in Table VII does not constitute a unified explanation in which a single theory with fixed parameters accounts for all observations simultaneously. This is a fair and important criticism of how the central claim is framed. We will revise the manuscript to reframe the contribution honestly: the paper demonstrates that the parameter space of f(R,T) gravity with the AV18 EoS, Bowers-Liang anisotropy, and magnetized matter is broad enough to accommodate mass-gap objects as neutron stars — i.e., that there exist values of λ, β, and B for which the modified TOV equations yield stable configurations with masses and radii consistent with individual observed compact objects including those in the mass gap. We will remove or substantially soften language suggesting a unified explanation. We will also add an explicit discussion of this limitation, noting that a single λ value consistent with all objects simultaneously would be required for a truly unified model, and that our results should be interpreted as a proof-of-principle demonstration rather than a definitive identification.","revision_made":"yes","referee_comment":"Table VII and surrounding text: λ is a fundamental coupling constant, not a per-object free parameter. Using different λ for different objects does not constitute a unified physical explanation."},{"response":"The referee is correct. The statement that the model 'simultaneously traverses the constraints' is not supported by Table VII, which shows individual a posteriori fitting with different parameter triples for each object. We will revise the text in Sec. III.A (around Fig. 6) and Sec. V to accurately describe what the table shows: that the explored parameter ranges (λ from 0 to −3, β from 0 to 1) collectively encompass the observational constraints, but no single parameter set reproduces all objects simultaneously. The word 'simultaneously' will be removed or replaced with 'collectively.'","revision_made":"yes","referee_comment":"Sec. III.A, text around Fig. 6: claim of 'simultaneous satisfaction' is contradicted by Table VII, where no single (λ, β) pair reproduces more than one or two objects."},{"response":"The referee is correct that the theoretical radius of 8.714 km for PSR J0740+6620 is significantly below the NICER constraint. We acknowledge this discrepancy, which we failed to discuss in the original manuscript. The small radius arises from the combination of the AV18 EoS (which is relatively soft) with the chosen magnetic field and anisotropy parameters. We will add a discussion of this discrepancy in the revised manuscript, noting that the model underpredicts the radius of PSR J0740+6620 at the parameter values used, and that this indicates the model cannot simultaneously reproduce both the mass and radius of this well-constrained NICER source. This further reinforces the need to soften the claims of consistency with observational data, as discussed in our response to the first comment. We will also add a column or note in Table VII indicating which objects have radius constraints and whether the theoretical radius falls within the observational error bars.","revision_made":"yes","referee_comment":"Table VII, PSR J0740+6620 row: theoretical radius 8.714 km is more than 5σ below the NICER constraint of 13.7^{+2.6}_{−1.5} km. The paper does not discuss this discrepancy."},{"response":"The referee raises a valid point. The expression R_Sch = (2GM/c²)(1 + 3λ/8π) is derived by matching the interior metric to the exterior Schwarzschild-like solution in f(R,T) gravity with the specific model f(R,T) = R + 2λT. However, the vacuum exterior solution in this model is not standard Schwarzschild, and the question of what constitutes the horizon condition in f(R,T) gravity requires careful treatment. We agree that using the modified R_Sch < R criterion as evidence against black-hole identification is circular to some degree, since the modification itself depends on λ. In the revised manuscript, we will: (i) add a discussion of this subtlety, (ii) note that for the standard GR Schwarzschild radius (2GM/c²), the criterion R > 2GM/c² is also satisfied for all our configurations (since 2GM/c² < R_Sch^{f(R,T)} < R for negative λ), so the conclusion that these objects are not black holes holds regardless of which criterion is used, and (iii) acknowledge that a rigorous determination of the horizon condition in f(R,T) gravity requires solving the full vacuum field equations, which is beyond the scope of this work.","revision_made":"yes","referee_comment":"Sec. IV, Eq. (39): The Schwarzschild radius in f(R,T) gravity is modified by the λ correction. The paper should discuss whether this modified R_Sch is the appropriate horizon condition, or whether the standard GR Schwarzschild radius should be used for the black-hole comparison."}],"tokens_in":25070,"tokens_out":1498,"duration_ms":77034,"standing_objections":["The fundamental issue raised in the first comment — that λ is a fundamental constant and should not vary per object — cannot be fully resolved within the current framework. While we can reframe the claims and soften the language, the paper as currently structured does not provide a single unified model with one λ value that reproduces all observed compact objects. A truly unified treatment would require either finding a single λ consistent with all observations (which our results suggest may not be possible with the AV18 EoS and Bowers-Liang anisotropy), or extending the model to include additional physics (e.g., a density-dependent coupling λ(ρ) or a more general f(R,T) functional form). We acknowledge this as a genuine limitation of the present work."]},"desk_editor":{"model":"glm-5.2","letter":"The main thing to know: this paper shows that f(R,T) = R + 2λT gravity with the AV18 EoS and Bowers-Liang anisotropy can produce neutron star masses up to ~3.3 M☉, which covers the mass-gap objects GW190814 (2.59 M☉) and GW200210 (2.83 M☉). The derivation is competent and the parameter exploration is systematic. But the headline claim — that mass-gap objects 'can be interpreted as neutron stars' — is overstated, because each object is fit with a different λ value, and λ is supposed to be a fundamental coupling constant, not a per-object tuning knob. The stress-test concern lands squarely here. Table VII tells the story: PSR J0740+6620 uses λ = −0.001 (essentially GR), while GW190814 needs λ = −3 and GW200210 needs λ = −2. No single λ reproduces both the well-constrained NICER sources and the mass-gap objects. The paper itself acknowledges model dependence in Sec. VI, but does not confront the deeper issue that varying a fundamental constant per object is not a physical explanation — it is parameter fitting without a statistical framework. What is done well: the EoS is microscopically motivated (LOCV + AV18), causality is verified (Fig. 3), the modified TOV equations (Eqs. 37–38) are derived consistently from the field equations, and the auxiliary quantities (Schwarzschild radius, compactness, redshift, Kretschmann scalar) are computed and shown to remain in physically reasonable ranges. The monotonicity check in Fig. 6 is a nice touch. The parameter tables are thorough. The soft spots, in proportion: (1) The per-object λ fitting is the central problem. The paper frames this as 'setting parameters to reproduce observations' but never addresses that a fundamental coupling constant cannot take different values for different stars. This is the load-bearing issue. (2) No stability analysis (radial perturbations) is provided for configurations reaching 3.3 M☉. For masses this far above the GR maximum, stability is not automatic and should be checked. (3) No code or data is shared, limiting reproducibility. (4) The radii predicted for several objects (e.g., ~8.7 km for PSR J0740+6620, which is observed at ~13.7 km) are inconsistent with observations, though the paper does not flag this. This paper is for researchers working on modified gravity applications to compact objects. It is a useful parameter-space exploration but not evidence that mass-gap objects are neutron stars. It deserves a serious referee who should require: (a) an explicit reframing as parameter-space exploration rather than physical interpretation, (b) a stability analysis for the high-mass branch, and (c) acknowledgment that no single parameter set works across all objects.","headline":"Paper derives modified TOV equations in f(R,T) gravity with AV18 EoS and anisotropy; can reach mass-gap masses but only via per-object parameter fitting with λ varying by three orders of magnitude.","tokens_in":26051,"tokens_out":1076,"would_cite":false,"duration_ms":74401,"reading_group":"no","serious_thinker":"no","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"glm-5.2","headline":"Modified gravity recasts mass-gap objects as neutron stars","keywords":["neutron stars","f(R,T) gravity","mass gap","equation of state","anisotropy","magnetic field","gravitational waves","modified gravity"],"falsifier":"A future gravitational-wave observation of a mass-gap object with a measured tidal deformability or moment of inertia inconsistent with any neutron-star equation of state—even allowing for modified gravity—would falsify the neutron-star interpretation. Alternatively, if independent constraints on λ from binary pulsar timing or solar-system tests force |λ| to be orders of magnitude smaller than the values used here (−1 to −3), the mass-enhancement mechanism collapses.","tokens_in":25268,"feed_emoji":"⭐","tokens_out":1436,"duration_ms":94810,"temperature":0.7,"pith_summary":"The paper argues that compact objects in the 2.5–5 solar-mass range—the so-called mass gap where conventional neutron-star equations of state in Einstein gravity cannot reach—can be reinterpreted as neutron stars if one works in the f(R,T) = R + 2λT framework of modified gravity, combined with a microscopic equation of state (AV18 nucleon-nucleon potential), Bowers-Liang pressure anisotropy, and strong density-dependent magnetic fields. The central mechanism is the coupling parameter λ: when λ takes negative values, pressure contributes to the effective gravitational mass, boosting the maximum mass a neutron star can sustain beyond what general relativity allows for the same equation of state. The anisotropy parameter β further increases masses and radii at fixed λ, while stronger surface magnetic fields soften the equation of state and reduce masses. By tuning (λ, β, B_surf), the authors reproduce the masses and radii of known pulsars (PSR J0740+6620, PSR J0952-0607), the binary merger GW170817, and—most strikingly—the secondary components of GW190814 (2.59 M☉) and GW200210-092254 (2.83 M☉), objects whose nature is otherwise unknown. The paper verifies that these configurations are not black holes by showing their Schwarzschild radii remain smaller than their stellar radii, their surface redshifts stay below 0.4, and the Kretschmann scalar remains finite everywhere.","feed_headline":"Modified gravity recasts mass-gap objects as neutron stars","feed_subtitle":"By coupling matter to geometry in f(R,T) gravity, neutron stars can reach 2.6–3.3 solar masses, potentially explaining GW190814's mysterious","key_machinery":"The modified TOV (Tolman-Oppenheimer-Volkoff) equations in f(R,T) = R + 2λT gravity, where the coupling parameter λ introduces an effective mass contribution from pressure (the m_f(R,T) term in the mass equation). The Bowers-Liang anisotropy model provides the pressure-splitting mechanism (Δ = β G/c^4 (εc^2 + P_r)(εc^2 + 3P_r) e^Ψ r^2). The AV18 nucleon-nucleon potential underlies the equation of state via the LOCV (lowest-order constrained variational) method. A Gaussian density-dependent magnetic field B(ρ) connects surface fields (10^16–10^17 G) to a central value (2×10^18 G).","core_discovery":"The paper's central claim is that the linear f(R,T) = R + 2λT modification to gravity, combined with anisotropy and magnetization, provides enough parameter freedom to support neutron-star configurations with masses up to roughly 3.3 solar masses—well into the mass gap—using a realistic microscopic equation of state that in standard general relativity caps out near 1.68 solar masses. The key lever is negative λ, which mixes pressure into the mass equation and enhances the maximum mass monotonically as λ becomes more negative. The authors then show that for each observed compact object, a specific combination of λ (ranging from 0 to −3), β (0 to 1), and surface magnetic field (5×10^16 to 10^5","pith_inferences":["The fact that no single (λ, β, B_surf) triple reproduces all observed compact objects simultaneously suggests either that the parameters are genuinely object-dependent (e.g., different neutron stars have different internal magnetic field topologies and anisotropy levels) or that the framework is functioning as a multi-parameter fit rather than a predictive theory. A joint Bayesian analysis across ","If λ is constrained by cosmological or solar-system tests to be far smaller than the values used here (|λ| << 0.001), then the mass-gap objects cannot be explained as neutron stars in this specific f(R,T) model, and the paper's mechanism would be effectively ruled out for the mass-gap problem.","The Bowers-Liang anisotropy model is a phenomenological prescription, not derived from microphysics; if alternative anisotropy models (e.g., Horvat or Herrera-Barreto) produce different mass-radius relations for the same λ, then the results may be sensitive to this choice in ways the paper does not explore."],"forward_implications":["If mass-gap objects like the GW190814 secondary are indeed neutron stars rather than black holes, their tidal deformability in future gravitational-wave events would differ markedly from black-hole predictions—potentially testable with next-generation detectors.","The f(R,T) coupling parameter λ, if it genuinely affects compact-star structure at the level claimed (λ ~ −1 to −3), would need to be reconciled with solar-system and binary-pulsar constraints on deviations from general relativity, which typically require λ to be extremely close to zero.","A single equation of state (AV18) plus three free parameters (λ, β, B_surf) can fit a wide range of observed masses and radii, but the paper fits each object with a different parameter triple—predictive power would require identifying a narrower allowed region or a correlation between the parameters that is physically motivated.","The finite Kretschmann scalar and sub-unity compactness for all mass-gap configurations provide a concrete criterion: if future observations measure compactness C > 1 or divergent curvature invariants for any mass-gap object, the neutron-star interpretation in this framework would fail."],"fun_headline_variants":["f(R,T) gravity pushes neutron star masses into the mass gap","f(R,T) gravity and anisotropy support 3.3 solar mass neutron stars","Modified gravity explains mass-gap objects as massive neutron stars","Magnetized neutron stars in f(R,T) gravity reach 3.3 solar masses","Negative coupling in f(R,T) gravity enables mass-gap neutron stars"],"cache_read_input_tokens":0,"weakest_assumption_plain":"Each observed compact object is matched with a different, independently chosen combination of the coupling parameter λ, the anisotropy parameter β, and the surface magnetic field, with no single parameter set reproducing all observations and no independent constraints on these parameters from other tests of gravity.","fun_headline_variants_meta":{"raw":{"variants":["f(R,T) gravity pushes neutron star masses into the mass gap","f(R,T) gravity and anisotropy support 3.3 solar mass neutron stars","Modified gravity explains mass-gap objects as massive neutron stars","Magnetized neutron stars in f(R,T) gravity reach 3.3 solar masses","Negative coupling in f(R,T) gravity enables mass-gap neutron stars","f(R,T) gravity extends neutron star mass limit into the mass gap","Realistic EoS and f(R,T) gravity yield 3.3 solar mass neutron stars"]},"model":"glm-5.2","effort":"high","cost_usd":0.0,"raw_usage":{"total_tokens":1215,"prompt_tokens":625,"completion_tokens":590,"prompt_tokens_details":null},"tokens_in":625,"tokens_out":590,"duration_ms":13784,"temperature":1.0,"reasoning_tokens":457,"cache_read_input_tokens":0,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-07T16:32:28.081836+00:00","model_set":{"reader":"glm-5.2"},"falsifier":"A future gravitational-wave observation of a mass-gap object with a measured tidal deformability or moment of inertia inconsistent with any neutron-star equation of state—even allowing for modified gravity—would falsify the neutron-star interpretation. Alternatively, if independent constraints on λ from binary pulsar timing or solar-system tests force |λ| to be orders of magnitude smaller than the values used here (−1 to −3), the mass-enhancement mechanism collapses.","supporting_citations":[],"review_version":1}