{"id":"3568a816-b9bb-43ee-b7bc-7ebf0b14d9e7","arxiv_id":"2508.20107","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"By fitting an f(T) power-law gravity model to chronometer, BBN, BAO, and supernova data, the authors report that the model can alleviate the Hubble constant tension and remains competitive with Lambda-CDM.","lead":"This paper tests a modified theory of gravity, called f(T) gravity, against modern cosmological data to see if it can resolve the Hubble tension. The results suggest this model fits the data well and might reduce the mismatch in measured expansion rates, offering a possible alternative to the standard cosmological model.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"SN Ia luminosity–G coupling is an untested phenomenological input; if removed or altered, the claimed H0 relief may disappear.","rationale":"The reader identified the same load-bearing assumption: the treatment of supernova luminosity and its dependence on G. My stress-test agrees and sharpens it: because H0 is measured primarily from SN Ia distances, any G-dependent rescaling of SN magnitudes directly alters the inferred H0. Without a physical derivation or independent calibration, the claimed tension relief may be an artifact of an extra model degree of freedom. However, since the full text is not available, I cannot determine whether the authors derive this coupling or show it is negligible. The reader's verdict of UNVERDICTED remains appropriate: the central claim is plausible but unverified. My concrete test is designed to settle the concern by isolating the effect of the G-coupling. I set verdict_should_be to UNCHANGED because my concern does not move the verdict away from UNVERDICTED—it reinforces the need for full-text scrutiny rather than establishing a decisive flaw.","tokens_in":829,"tokens_out":2003,"duration_ms":25710,"concrete_test":"Reanalyze the same combined data (cosmic chronometers, BBN, DESI BAO, SNe Ia) with the same f(T) power-law model but fix the SN Ia absolute magnitude to a standard, G-independent calibration (e.g., a free constant, as in ΛCDM). Compare the H0 posterior to the original result and to the SH0ES measurement. If the H0 constraint no longer overlaps the late-universe value, the claimed H0-tension relief is driven by the assumed G-coupling rather than by f(T) perturbation theory. Additionally, independently derive the expected SN Ia luminosity–G scaling from a specific explosion model (e.g., 56Ni mass as a function of G) and check whether the resulting M is consistent with existing distance-ladder calibrations.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—that f(T) gravity alleviates the H0 tension—rests on more than the power-law form of f(T). It also relies on the statement that 'the evolution of the supernova luminosity and its dependence on the gravitational constant are considered to refine the measurement of cosmological parameters.' This is not a minor detail: Type Ia supernova absolute magnitudes are empirically calibrated (e.g., via Cepheids or TRGB). Introducing a dependence of the peak luminosity on the effective gravitational constant G_eff changes the distance modulus for every SN Ia, which directly shifts the inferred H0. The abstract gives no functional form, sign, or magnitude for this coupling, and does not indicate whether it is derived from a physical model of the explosion mechanism or simply inserted as a phenomenological free function. If the coupling is arbitrary, then the H0 shift is not a prediction of f(T) gravity but an extra degree of freedom in the likelihood. The paper's information-criteria comparison to ΛCDM would then be comparing a model with an additional adjustable effect, which could trivially improve the fit. Because the full derivation of the perturbation equations is unavailable in this abstract-only review, the modified Poisson/lensing equations cannot be checked either. But the SN luminosity–G coupling is the most load-bearing unverified ingredient, since it directly enters the key observable used to measure H0. A mismatch between this assumed coupling and independent SN-calibration data would invalidate the claimed tension relief.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper claims to test a power-law f(T) gravity model against cosmological observations (cosmic chronometers, BBN, DESI BAO, Type Ia supernovae), including scalar perturbations that modify the Poisson and lensing equations. It reports constraints on the f(T) parameters and suggests that the model can alleviate the H0 tension, in part because the supernova luminosity is assumed to evolve with the gravitational constant. The paper concludes by comparing the f(T) model with ΛCDM using information criteria.","tokens_in":1183,"tokens_out":2865,"duration_ms":37598,"significance":"If the technical derivations and data analysis are correct, the paper would provide a useful, multi-probe comparison of a specific f(T) model to ΛCDM, with the notable feature of a physically motivated (or at least phenomenologically explicit) coupling between SN Ia luminosity and the gravitational constant. The use of multiple datasets and model-comparison statistics is a strength. However, the significance is currently difficult to assess because the abstract does not provide the perturbation equations, the functional form of the SN luminosity–G coupling, or any numerical results with uncertainties. The central claim about alleviating the H0 tension is plausible but not yet independently supported. The paper's cautious language is appropriate, but the abstract alone does not establish that the alleviation is a prediction rather than a post-fit property.","major_comments":[{"comment":"The statement that 'the evolution of the supernova luminosity and its dependence on the gravitational constant are considered' is load-bearing for the H0 result, but the abstract gives no functional form, sign, magnitude, or physical justification for this coupling. SN Ia absolute magnitudes are empirically calibrated; introducing a G_eff dependence changes every distance modulus and therefore shifts H0 directly. If this coupling is a free phenomenological function, the comparison with ΛCDM via information criteria is not meaningful unless the extra degrees of freedom and their priors are fully specified. The authors must state whether this coupling is derived from a physical model of the explosion mechanism or is a phenomenological ansatz, and if the latter, how it is constrained independently of the H0 measurement.","section":"Abstract, fourth sentence"},{"comment":"The model parameters are fitted to the same data (SNe Ia, BAO, etc.) that are later used to assess whether the model 'alleviates' the H0 tension. This is a circularity concern: the reduced tension is a property of the best-fit model, not an independent prediction. To support the claim, the authors should provide an out-of-sample test, a prior-predictive check, or a clear demonstration that the model's H0 inference is driven by a subset of the data that is not also used to fit the f(T) parameters. Without such a check, the statement that f(T) 'offers a viable alternative' is not stronger than saying the model can be made to fit the combined data.","section":"Abstract, last sentences"},{"comment":"The central technical claim is that scalar perturbations in f(T) gravity modify the Poisson and lensing equations and thereby affect cosmological observables. No equations, approximation schemes, or gauge choices are given in the abstract, and I was not provided with the full text. I cannot verify whether the modified perturbation equations are consistently derived, whether the quasistatic approximation is valid, or whether the lensing potential is treated correctly. Because the entire phenomenological impact of f(T) flows through these equations, this is a blocking issue for the present review: the manuscript's core derivation must be available and checked before the claims can be evaluated.","section":"Abstract, first two sentences"}],"minor_comments":[{"comment":"The phrase 'cosmic chromatometers' appears to be a typo for 'cosmic chronometers.' Please correct.","section":"Abstract, first sentence"},{"comment":"The information criteria are not named. Please specify which criteria are used (e.g., AIC, BIC, DIC) so that the comparison is reproducible from the abstract.","section":"Abstract, fourth sentence"},{"comment":"The abstract reports no numerical values, uncertainties, or significance levels. While this is common for an abstract, including a central H0 value and its credible interval would help readers assess the claimed tension alleviation.","section":"Abstract"}],"recommendation":"uncertain","confidential_remarks":"This review is based solely on the abstract because the full text was not provided. The technical core of the paper—scalar perturbations, the SN luminosity–G coupling, and the information-criteria comparison—cannot be checked from the abstract alone. I recommend that the editor obtain and send the full manuscript before making a decision. The stress-test concern about the SN Ia luminosity–G coupling appears valid and should be addressed explicitly by the authors."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThe abstract is a classic case of a plausible data-fitting claim that cannot be evaluated without the supplement. The genuinely new bit is the combination of f(T) scalar perturbations with DESI BAO, cosmic chronometers, BBN, and SNe, plus the explicit decision to let SN luminosity depend on the effective gravitational constant. That last ingredient is exactly where the load-bearing tension relief comes from, and the abstract gives no functional form, no derivation, and no independent test. If that coupling is a free function fitted to the same SN data used to measure H0, the comparison to ΛCDM is stacked. If it is derived from the f(T) action or a maverick explosion model, it's a nontrivial contribution. We cannot tell from the abstract.\n\nWhat the paper does well, as far as the abstract indicates: it engages with current data releases (DESI BAO), uses several information criteria for model comparison, and frames the H0 question as a test of modified gravity rather than a curiosity. That is the right way to sell f(T). The perturbation equations for modified Poisson/lensing are not new but applying them to a broad dataset is a service to the field.\n\nThe soft spots: no error bars on the parameter estimates in the abstract, no description of the likelihood or priors, and no statement about whether the SN luminosity–G coupling is a one-parameter extension of the standard absolute magnitude or a full model. The stress-test concern is the one to send the referee after: make them write down M(G_eff) explicitly and show that the H0 relief is not an artifact of that choice. If the coupling is phenomenological, the model has one more parameter than ΛCDM and the information criteria need to reflect that honestly.\n\nOverall, this is a paper that deserves a serious referee, but the referee should be instructed to treat the SN luminosity coupling as the central issue, not the f(T) power-law exponent. If the coupling holds up, the paper is a legitimate entry in the modified-gravity cookbook. If not, it's another example of fitting one's way out of the tension.\n\nI'd bring it to reading group if the full text is available, but I wouldn't cite the abstract as evidence. Send it to peer review.","headline":"The H0 claim hinges on an unspecified SN luminosity–G_eff coupling, so the abstract is a plausible but unverified candidate for peer review.","tokens_in":1623,"tokens_out":2294,"would_cite":false,"duration_ms":26779,"reading_group":"maybe","serious_thinker":"unclear","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["04.50.Kd","98.80.-k","95.36.+x"],"model":"deepseek-v4-flash","headline":"This analysis claims that power-law f(T) modified gravity, with supernova luminosity tied to the gravitational constant, reduces the Hubble tension while remaining competitive with Lambda-CDM.","keywords":["f(T) gravity","Hubble tension","Teleparallel gravity","Poisson equation","supernova luminosity","baryon acoustic oscillations","cosmic chronometers","dark energy"],"falsifier":"Measure the luminosity distance using gravitational-wave standard sirens at redshifts around 0.1–1, which do not rely on a varying gravitational constant for their calibration, and compare with the distances the f(T) model predicts from supernova brightness. If the G-dependent supernova calibration is wrong, the inferred H0 from sirens would disagree with the paper's H0; conversely, if an independent H0 measurement with f(T) corrections still differs from late-universe estimates by more than the standard significance, the tension is not actually resolved.","tokens_in":770,"feed_emoji":"🔭","tokens_out":5414,"duration_ms":59130,"temperature":0.7,"pith_summary":"This paper is trying to establish that a particular modification of gravity—power-law f(T) teleparallel gravity—can reduce the mismatch between early- and late-universe values of the Hubble constant. The authors fit the model to combined cosmological data covering cosmic chronometers, primordial nucleosynthesis, baryon acoustic oscillations, and Type Ia supernovae, and find it statistically competitive with the standard Lambda-CDM model. They also fold in a proposed dependence of supernova luminosity on the gravitational constant, which changes how distances and H0 are inferred. If the model is right, modified gravity offers a live alternative to dark energy as the explanation of late-time acceleration.","feed_headline":"Modified gravity eases the Hubble tension, data fit claims","feed_subtitle":"Fitting power-law f(T) gravity to BAO, chronometers, SNe and BBN yields H0 closer to local measurements than Lambda-CDM.","key_machinery":"The load-bearing object is the power-law f(T) model of teleparallel gravity, an extension of the teleparallel equivalent of general relativity in which the torsion scalar T is replaced by a power-law function, so gravity deviates from GR at late times. The scalar perturbations of this model alter the Poisson and lensing equations, effectively changing the gravitational constant that governs structure growth; in parallel, the paper treats Type Ia supernova luminosity as dependent on that same gravitational constant, which modifies the distance ladder used to measure H0. These two channels—growth and standard-candle brightness—are what carry the tension relief.","core_discovery":"The claimed discovery is that scalar perturbations in f(T) gravity modify the Poisson and lensing equations, and this modification—combined with a gravitational-constant-dependent supernova luminosity—lets the model bring cosmological observations into better agreement than Lambda-CDM does on the H0 front. On the paper's own terms, the power-law f(T) model, constrained by cosmic chronometers, BBN, BAO, and SNe Ia, yields cosmological parameters that relieve the Hubble tension without discarding the concordance picture, and model-selection criteria indicate it remains a viable alternative to Lambda-CDM.","pith_inferences":["If the G-dependent supernova calibration is the main mechanism easing H0, then independent distance indicators that do not rely on that calibration—such as gravitational-wave standard sirens—should reproduce the same H0; a mismatch would isolate the assumption.","The same modified Poisson equation that eases H0 also changes the predicted growth rate of cosmic structure, so growth measurements (e.g., redshift-space distortions) should show a departure from Lambda-CDM in the same parameter region; this is a testable extension the paper does not perform.","By making SN Ia absolute magnitude a function of G, the model predicts a subtle redshift drift in standardized supernova brightness; stacking large SNe samples by redshift could detect this directly."],"forward_implications":["If f(T) gravity is right, the Hubble tension is not a sign that the standard model is broken; it is a sign that gravity itself changes the way distances are inferred, and the fitted f(T) parameters supply the correction.","Combined fits become the testing ground: a power-law f(T) model constrained by chronometers, BBN, BAO, and SNe Ia can serve as a baseline for future surveys instead of Lambda-CDM.","Supernova catalogues would need recalibration for a time-varying gravitational constant; reported H0 from SNe Ia would shift depending on the f(T) parameters.","Information-criterion comparisons give a quantitative, model-selection way to judge when modified gravity is preferred over dark energy."],"supporting_citations":[],"fun_headline_variants":["f(T) gravity eases Hubble tension in new data fit","Modified gravity offers viable fix for Hubble tension","f(T) model relieves H0 discrepancy, study finds","Power-law f(T) gravity beats LCDM on H0 tension","f(T) gravity challenges LCDM with better H0 fit"],"cache_read_input_tokens":2816,"weakest_assumption_plain":"The whole fit rests on the chosen power-law form of f(T) and on the assumption that Type Ia supernova brightness changes with the gravitational constant; if that coupling is wrong, the fitted parameters and the claimed H0 relief shift.","fun_headline_variants_meta":{"raw":{"variants":["f(T) gravity eases Hubble tension in new data fit","Modified gravity offers viable fix for Hubble tension","f(T) model relieves H0 discrepancy, study finds","Power-law f(T) gravity beats LCDM on H0 tension","f(T) gravity challenges LCDM with better H0 fit"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000454,"raw_usage":{"total_tokens":2139,"prompt_tokens":783,"completion_tokens":1356,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":527,"completion_tokens_details":{"reasoning_tokens":1287}},"tokens_in":527,"tokens_out":1356,"duration_ms":9065,"temperature":1.0,"reasoning_tokens":1287,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-05T20:52:00.687320+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the luminosity distance using gravitational-wave standard sirens at redshifts around 0.1–1, which do not rely on a varying gravitational constant for their calibration, and compare with the distances the f(T) model predicts from supernova brightness. If the G-dependent supernova calibration is wrong, the inferred H0 from sirens would disagree with the paper's H0; conversely, if an independent H0 measurement with f(T) corrections still differs from late-universe estimates by more than the standard significance, the tension is not actually resolved.","supporting_citations":[],"review_version":1}