arxiv: 2604.24761 · v1 · submitted 2026-04-27 · 🌌 astro-ph.CO

Recognition: unknown

Cosmological Impact of Redshift-Dependent Type Ia Supernovae Calibration

Seyed Hamidreza Mirpoorian , Meng-Xiang Lin , Levon Pogosian

Authors on Pith no claims yet

Pith reviewed 2026-05-08 01:27 UTC · model grok-4.3

classification 🌌 astro-ph.CO

keywords Type Ia supernovaeHubble tensiondynamical dark energycosmological calibrationredshift dependenceSNIa standardizationdark energy equation of state

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The pith

A redshift-dependent calibration correction to Type Ia supernovae is preferred at 4.3 sigma in dynamical dark energy models and reduces the Hubble tension to 1.5 sigma.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The authors introduce a phenomenological correction to the observed magnitudes of Type Ia supernovae that grows in proportion to cosmic look-back time and test whether this single free amplitude affects inferences about the universe's expansion history. They fit the correction simultaneously with standard cosmological parameters to combinations of cosmic microwave background, baryon acoustic oscillation, and supernova data. In the standard Lambda CDM model the correction is not required by the data and leaves other parameters essentially unchanged. When dark energy is allowed to evolve and a local distance-ladder prior on the supernova absolute magnitude is included, however, the correction becomes strongly preferred and brings the locally measured Hubble constant into agreement with early-universe constraints. The best-fitting model in this extended case behaves like a constant dark-energy equation of state with w less than negative one.

Core claim

We find no evidence for a redshift-dependent calibration effect when fitting uncalibrated SNIa data, and its inclusion has a negligible impact on cosmological parameters within Lambda CDM. When incorporating a prior on the SNIa absolute magnitude from SH0ES, a nonzero calibration parameter is weakly preferred within Lambda CDM. With dynamical dark energy, the preference of a nonzero calibration parameter increases to 4.3 sigma, and it can accommodate both the distance ladder and early-Universe constraints, reducing the Hubble tension to 1.5 sigma, with the best-fit model effectively corresponding to a constant equation of state with w less than negative one.

What carries the argument

A single free amplitude that multiplies a correction to SNIa magnitudes scaling with cosmic look-back time.

If this is right

In Lambda CDM the calibration correction has negligible impact on other cosmological parameters.
With the SH0ES prior on absolute magnitude, a nonzero calibration amplitude is weakly preferred inside Lambda CDM.
In dynamical dark energy models the same amplitude is preferred at 4.3 sigma and reconciles local and early-universe measurements of the expansion rate.
The preferred dynamical dark energy solution behaves like a constant equation of state with w less than negative one.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Future wide-field supernova surveys reaching z greater than 1 can directly test whether the look-back-time scaling persists.
If the effect is confirmed, supernova standardization procedures may need to incorporate explicit redshift dependence in addition to host-galaxy corrections.
The result suggests that simultaneous extensions to both supernova calibration and the dark-energy sector may be necessary to resolve remaining tensions.
The approach could be cross-checked by combining the same supernova sample with gravitational-wave standard sirens at comparable redshifts.

Load-bearing premise

Any redshift-dependent calibration effect in Type Ia supernovae can be captured by a single amplitude that scales with look-back time and does not depend on progenitor age or other variables.

What would settle it

High-redshift supernova observations that constrain the amplitude of the look-back-time scaling correction to be consistent with zero at greater than 3 sigma significance.

Figures

Figures reproduced from arXiv: 2604.24761 by Levon Pogosian, Meng-Xiang Lin, Seyed Hamidreza Mirpoorian.

**Figure 1.** Figure 1: FIG. 1. The 68% and 95% confidence contours and the corresponding one-dimensional marginalized posterior distributions for view at source ↗

**Figure 2.** Figure 2: FIG. 2. The luminosity distances predicted by the view at source ↗

read the original abstract

Type Ia supernovae (SNIa) play a central role in constraining the late-time expansion history of the Universe and are directly implicated in current cosmological tensions. Motivated by the possibility of unaccounted redshift-dependent calibration systematics or new physics, we investigate the impact of a phenomenological correction to SNIa magnitudes that scales with cosmic look-back time. We parameterize this effect with a free amplitude and constrain it using a combination of cosmic microwave background, baryon acoustic oscillation, and SNIa data, considering both $\Lambda$CDM and dynamical dark energy models. Importantly, our parameterization is not intended to serve as a proxy for SNIa progenitor age, as current observations show no significant difference in standardized SNIa brightness between young and old progenitor populations at low redshift. We find no evidence for a redshift-dependent calibration effect when fitting uncalibrated SNIa data, and its inclusion has a negligible impact on cosmological parameters within $\Lambda$CDM, nor does it qualitatively change the inferred dynamics of evolving dark energy. When incorporating a prior on the SNIa absolute magnitude from SH0ES, a nonzero calibration parameter is weakly preferred within $\Lambda$CDM. Interestingly, with dynamical dark energy, the preference of a nonzero calibration parameter increases to $4.3\sigma$, and it can accommodate both the distance ladder and early-Universe constraints, reducing the Hubble tension to $1.5\sigma$, with the best-fit model effectively corresponding to a constant equation of state with $w < -1$. Overall, our results indicate that redshift-dependent SNIa calibration effects, as parameterized here, are not supported by current data within $\Lambda$CDM, but can play a role in reconciling cosmological datasets when combined with extensions to the late-time expansion history.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper shows a 4.3 sigma preference for nonzero look-back-time scaling in SNIa magnitudes only after adding the SH0ES prior and dynamical dark energy, dropping the Hubble tension to 1.5 sigma, but the result rests on a single-parameter form and the same data driving the original discrepancy.

read the letter

This paper adds a phenomenological amplitude that scales SNIa magnitudes with cosmic look-back time and fits it jointly with cosmological parameters from CMB, BAO, and supernova data. Without the SH0ES prior the amplitude stays consistent with zero in both LCDM and dynamical dark energy, with negligible shifts in other parameters. Once the local absolute-magnitude prior is included, the amplitude becomes preferred at 4.3 sigma in the dynamical dark energy case, the tension falls to 1.5 sigma, and the best-fit dark energy behavior looks like a constant w below -1. That interplay between the calibration term and the dark energy extension is the clearest new piece here. The authors are explicit that the term is not meant to stand in for progenitor-age effects, citing low-redshift data showing no brightness difference. The fits themselves follow standard combinations and report concrete significance numbers. The main limitation is that a single linear look-back-time amplitude may miss other redshift-dependent systematics tied to host-galaxy properties, metallicity, or selection at higher redshifts. The reported preference also appears only after folding in the SH0ES constraint that defines the tension, so the exercise is more a test of consistency than an independent resolution. I would have liked to see checks against alternative functional forms or splits by host properties to gauge how much the result depends on the exact parameterization chosen. This work is aimed at researchers following the Hubble tension and supernova calibration questions. Anyone running joint fits with extended dark energy models will find the reported numbers and the way the calibration term trades off with w useful to compare against. It is solid enough to deserve referee time, mainly to verify the likelihood implementation and to push on the robustness of the single-parameter assumption.

Referee Report

2 major / 2 minor

Summary. The manuscript examines a phenomenological redshift-dependent correction to Type Ia supernovae magnitudes, parameterized by a single free amplitude that scales linearly with cosmic look-back time. Fits to CMB, BAO, and SNIa data show no evidence for this effect in ΛCDM without external priors and negligible impact on cosmological parameters. With a SH0ES prior on the absolute magnitude, a nonzero amplitude is weakly preferred in ΛCDM; in dynamical dark energy models the preference reaches 4.3σ, the model accommodates both distance-ladder and early-Universe constraints, the Hubble tension drops to 1.5σ, and the best-fit corresponds to a constant equation of state w < -1.

Significance. If the results hold, the work illustrates how a simple redshift-dependent SNIa calibration term can interact with late-time dark-energy extensions to ease the Hubble tension. This underscores the value of testing whether apparent tensions arise partly from unmodeled calibration trends rather than new physics alone. No machine-checked proofs or fully reproducible code releases are described, but the analysis is explicitly data-driven and falsifiable through future SNIa samples.

major comments (2)

[Abstract and §2] Abstract and §2 (parameterization): the central claim that a nonzero calibration amplitude is preferred at 4.3σ and reduces the Hubble tension to 1.5σ rests on the assumption that any redshift-dependent calibration effect is fully captured by a single amplitude scaling linearly with look-back time. This functional form is not shown to be robust against correlations with host-galaxy properties, metallicity, or selection effects that also vary with redshift, which directly affects whether the reported tension reduction is physical or an artifact of the restrictive parameterization.
[§4] §4 (results with SH0ES prior): the 4.3σ preference and 1.5σ tension reduction appear only after imposing the SH0ES prior on the SNIa absolute magnitude. Because this prior is itself derived from the same low-redshift SNIa sample used in the fit, the manuscript must demonstrate that the amplitude preference is not driven by the prior rather than by the high-redshift data; without such a test the claim that the correction “accommodates both the distance ladder and early-Universe constraints” remains load-bearing and under-supported.

minor comments (2)

[Abstract] Abstract: the term “uncalibrated SNIa data” is used without a precise definition; clarify whether it refers to data lacking an absolute-magnitude anchor or to data with only relative calibration.
[Figure captions and §3] Figure captions and §3: ensure that the look-back-time scaling is plotted or tabulated explicitly so readers can judge the magnitude of the correction at z ≈ 1.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed comments on our manuscript. We address each major comment point by point below, providing the strongest honest defense of our analysis while indicating where revisions will be made to improve clarity and robustness.

read point-by-point responses

Referee: [Abstract and §2] Abstract and §2 (parameterization): the central claim that a nonzero calibration amplitude is preferred at 4.3σ and reduces the Hubble tension to 1.5σ rests on the assumption that any redshift-dependent calibration effect is fully captured by a single amplitude scaling linearly with cosmic look-back time. This functional form is not shown to be robust against correlations with host-galaxy properties, metallicity, or selection effects that also vary with redshift, which directly affects whether the reported tension reduction is physical or an artifact of the restrictive parameterization.

Authors: We thank the referee for this important observation. Our parameterization is explicitly phenomenological and minimal, as stated in the manuscript: it is designed to test for the presence of any linear trend in SNIa magnitude corrections with look-back time rather than to model all possible redshift-dependent systematics. The manuscript already notes that the form is not intended as a proxy for progenitor age effects, which show no significant difference in standardized brightness at low redshift. While correlations with host-galaxy properties or selection effects could in principle be present, the data yield no evidence for a nonzero amplitude in ΛCDM, and the 4.3σ preference appears only when combined with dynamical dark energy. We will revise §2 to add an explicit discussion of these limitations, stating that the results apply specifically to this functional form and that more detailed modeling of host correlations would be a valuable extension. This does not alter the reported statistical results under the assumed parameterization. revision: partial
Referee: [§4] §4 (results with SH0ES prior): the 4.3σ preference and 1.5σ tension reduction appear only after imposing the SH0ES prior on the SNIa absolute magnitude. Because this prior is itself derived from the same low-redshift SNIa sample used in the fit, the manuscript must demonstrate that the amplitude preference is not driven by the prior rather than by the high-redshift data; without such a test the claim that the correction “accommodates both the distance ladder and early-Universe constraints” remains load-bearing and under-supported.

Authors: We agree that demonstrating the role of the high-redshift data is essential. The SH0ES prior constrains only the absolute magnitude M_B, which is independent of the additional redshift-dependent calibration amplitude. Without this prior, the calibration amplitude remains consistent with zero in both ΛCDM and dynamical dark energy models. The increased preference to 4.3σ in the dynamical dark energy case arises from the joint fit, where the extended late-time expansion allows the high-redshift SNIa to pull the calibration parameter away from zero while remaining consistent with CMB and BAO. To address the referee's concern directly, we will add a new test in the revised §4 (or an appendix) that applies the SH0ES prior exclusively to the low-redshift anchor subsample and constrains the calibration amplitude using primarily the high-redshift SNIa (z > 0.1) together with CMB and BAO. This will show the contribution of the high-redshift data to the reported preference and tension reduction. revision: yes

Circularity Check

0 steps flagged

No significant circularity; results are data-driven fits of a free phenomenological parameter

full rationale

The paper introduces a single free amplitude for a look-back-time scaling correction to SNIa magnitudes and constrains it via standard MCMC fits to CMB+BAO+SNIa (with optional SH0ES prior). Reported significances (e.g., 4.3σ preference) and tension reductions are direct outputs of these fits rather than algebraic reductions of the input data or self-citations. No load-bearing self-citation, uniqueness theorem, or ansatz smuggling is present in the abstract or described methodology; the parameterization is explicitly stated as phenomenological and not a proxy for progenitor effects. The derivation chain is therefore self-contained and externally falsifiable against the same datasets.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on one new free parameter for the calibration amplitude plus standard cosmological model assumptions; no new particles or forces are postulated.

free parameters (1)

redshift-dependent calibration amplitude
Free parameter controlling the strength of the look-back time scaling correction to SNIa magnitudes; its value is fitted to data.

axioms (2)

ad hoc to paper Any redshift-dependent calibration effect scales linearly with cosmic look-back time
This is the explicit phenomenological form introduced for the correction.
domain assumption Standard flat background cosmology (ΛCDM or wCDM) with usual parameter priors
Used as the base models for all fits.

pith-pipeline@v0.9.0 · 5629 in / 1466 out tokens · 55293 ms · 2026-05-08T01:27:35.713287+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

39 extracted references · 37 canonical work pages · 12 internal anchors

[1]

Leauthaud and A

A. Leauthaud and A. Riess, Nature Astron.9, 1123 (2025), arXiv:2509.00359 [astro-ph.CO]

work page arXiv 2025
[2]

Planck 2018 results. VI. Cosmological parameters

N. Aghanimet al.(Planck), Astron. Astrophys.641, A6 (2020), arXiv:1807.06209 [astro-ph.CO]

work page internal anchor Pith review arXiv 2020
[3]

SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field

E. Camphuiset al.(SPT-3G), Phys. Rev. D113, 083504 (2026), arXiv:2506.20707 [astro-ph.CO]

work page internal anchor Pith review arXiv 2026
[4]

A. G. Riesset al., Astrophys. J. Lett.934, L7 (2022), arXiv:2112.04510 [astro-ph.CO]

work page internal anchor Pith review arXiv 2022
[5]

Breuval, A.G

L. Breuval, A. G. Riess, S. Casertano, W. Yuan, L. M. Macri, M. Romaniello, Y. S. Murakami, D. Scolnic, G. S. Anand, and I. Soszy´ nski, Astrophys. J.973, 30 (2024), arXiv:2404.08038 [astro-ph.CO]

work page arXiv 2024
[6]

DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints

M. Abdul Karimet al.(DESI), Phys. Rev. D112, 083515 (2025), arXiv:2503.14738 [astro-ph.CO]

work page internal anchor Pith review arXiv 2025
[7]

Kamionkowski and A

M. Kamionkowski and A. G. Riess, Ann. Rev. Nucl. Part. Sci.73, 153 (2023), arXiv:2211.04492 [astro-ph.CO]

work page arXiv 2023
[8]

The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics

E. Di Valentinoet al.(CosmoVerse Network), Phys. Dark Univ.49, 101965 (2025), arXiv:2504.01669 [astro-ph.CO]

work page internal anchor Pith review arXiv 2025
[9]

Y. Cai, X. Ren, T. Qiu, M. Li, and X. Zhang 10.1093/nsr/nwag115 (2025), arXiv:2505.24732 [astro- ph.CO]

work page internal anchor Pith review Pith/arXiv arXiv doi:10.1093/nsr/nwag115 2025
[10]

Arza et al.,The COSMIC WISPers White Paper: The physics case for Weakly Interacting Slim Particles, 2603.03433

A. Arzaet al., (2026), arXiv:2603.03433 [hep-ph]

work page arXiv 2026
[11]

M. M. Phillips, Astrophys. J. Lett.413, L105 (1993)

1993
[12]

A. G. Riess, W. H. Press, and R. P. Kirshner, Astrophys. J.473, 88 (1996), arXiv:astro-ph/9604143

work page arXiv 1996
[13]

Tripp, Astron

R. Tripp, Astron. Astrophys.331, 815 (1998)

1998
[14]

Still Accelerating: Type Ia supernova cosmology is robust to host galaxy age evolution

P. Wisemanet al., (2026), arXiv:2601.13785 [astro- ph.CO]

work page internal anchor Pith review arXiv 2026
[15]

Old Universe, Young SNe Ia: A Statistical Analysis of Type Ia Supernova Progenitor Age from 6,983 TITAN Host Galaxies, and Implications for Cosmology

Y. Murakamiet al., (2026), arXiv:2604.16597 [astro- ph.CO]

work page internal anchor Pith review Pith/arXiv arXiv 2026
[16]

Amendola, P

L. Amendola, P. S. Corasaniti, and F. Occhionero, (1999), arXiv:astro-ph/9907222

work page internal anchor Pith review arXiv 1999
[17]

B. S. Wright and B. Li, Phys. Rev. D97, 083505 (2018), arXiv:1710.07018 [astro-ph.CO]

work page arXiv 2018
[18]

Rathore, S

Ruchika, H. Rathore, S. Roy Choudhury, and V. Rentala, JCAP06, 056, arXiv:2306.05450 [astro-ph.CO]

work page arXiv
[19]

Sakstein, H

J. Sakstein, H. Desmond, and B. Jain, Phys. Rev. D100, 104035 (2019), arXiv:1907.03775 [astro-ph.CO]

work page arXiv 2019
[20]

Son, Y.-W

J. Son, Y.-W. Lee, C. Chung, S. Park, and H. Cho, (2025), arXiv:2510.13121 [astro-ph.CO]

work page arXiv 2025
[21]

Popovic and M

B. Popovic and M. Sullivan, (2026), arXiv:2602.12822 [astro-ph.CO]

work page arXiv 2026
[22]

Cobaya: Code for Bayesian Analysis of hierarchical physical models

J. Torrado and A. Lewis, JCAP05, 057, arXiv:2005.05290 [astro-ph.IM]

work page internal anchor Pith review arXiv 2005
[23]

Efficient Computation of CMB anisotropies in closed FRW models

A. Lewis, A. Challinor, and A. Lasenby, Astrophys. J. 538, 473 (2000), arXiv:astro-ph/9911177

work page Pith review arXiv 2000
[24]

Accelerating Universes with Scaling Dark Matter

M. Chevallier and D. Polarski, Int. J. Mod. Phys. D10, 213 (2001), arXiv:gr-qc/0009008

work page Pith review arXiv 2001
[25]

E. V. Linder, Phys. Rev. Lett.90, 091301 (2003), arXiv:astro-ph/0208512

work page Pith review arXiv 2003
[26]

Aghanim et al

N. Aghanimet al.(Planck), Astron. Astrophys.641, A5 (2020), arXiv:1907.12875 [astro-ph.CO]

work page arXiv 2020
[27]

Efstathiou and S

G. Efstathiou and S. Gratton4, 10.21105/as- tro.1910.00483 (2019), arXiv:1910.00483 [astro-ph.CO]

work page doi:10.21105/as- 1910
[28]

Rosenberg, S

E. Rosenberg, S. Gratton, and G. Efstathiou, Mon. Not. Roy. Astron. Soc.517, 4620 (2022), arXiv:2205.10869 [astro-ph.CO]

work page arXiv 2022
[29]

Carron, M

J. Carron, M. Mirmelstein, and A. Lewis, JCAP09, 039, arXiv:2206.07773 [astro-ph.CO]

work page arXiv
[30]

M. S. Madhavacherilet al.(ACT), Astrophys. J.962, 113 (2024), arXiv:2304.05203 [astro-ph.CO]

work page arXiv 2024
[31]

F. J. Quet al.(ACT), Astrophys. J.962, 112 (2024), arXiv:2304.05202 [astro-ph.CO]

work page arXiv 2024
[32]

Hahn, M.J

C. Hahnet al., Astron. J.165, 253 (2023), arXiv:2208.08512 [astro-ph.CO]

work page arXiv 2023
[33]

Zhouet al.(DESI), Astron

R. Zhouet al.(DESI), Astron. J.165, 58 (2023), arXiv:2208.08515 [astro-ph.CO]

work page arXiv 2023
[34]

Raichoor, J

A. Raichooret al., Astron. J.165, 126 (2023), arXiv:2208.08513 [astro-ph.CO]

work page arXiv 2023
[35]

Chaussidon, C

E. Chaussidonet al., Astrophys. J.944, 107 (2023), arXiv:2208.08511 [astro-ph.CO]

work page arXiv 2023
[36]

The Pantheon+ Analysis: The Full Dataset and Light-Curve Release

D. Scolnicet al., Astrophys. J.938, 113 (2022), arXiv:2112.03863 [astro-ph.CO]

work page internal anchor Pith review arXiv 2022
[37]

The Pantheon+ Analysis: Cosmological Constraints

D. Broutet al., Astrophys. J.938, 110 (2022), arXiv:2202.04077 [astro-ph.CO]

work page internal anchor Pith review arXiv 2022
[38]

Pogosian, M

L. Pogosian, M. Raveri, K. Koyama, M. Martinelli, A. Sil- vestri, G.-B. Zhao, J. Li, S. Peirone, and A. Zucca, Nature Astron.6, 1484 (2022), arXiv:2107.12992 [astro-ph.CO]

work page arXiv 2022
[39]

Poulin, T.L

V. Poulin, T. L. Smith, R. Calder´ on, and T. Simon, Phys. Rev. D111, 083552 (2025), arXiv:2407.18292 [astro- ph.CO]

work page arXiv 2025