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arxiv: 2606.09650 · v1 · pith:6L6ZCGOSnew · submitted 2026-06-08 · 🌌 astro-ph.CO · gr-qc· hep-ph

Pantheon+ supernovae corrected for progenitor age indicate the universe is decelerating

Pith reviewed 2026-06-27 15:41 UTC · model grok-4.3

classification 🌌 astro-ph.CO gr-qchep-ph
keywords Type Ia supernovaePantheon+ cataloguedeceleration parameterprogenitor agecosmographydipole anisotropycosmic acceleration
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The pith

Applying progenitor age corrections to Pantheon+ supernovae shifts the large-scale monopole of q0 to positive values, indicating deceleration.

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

The paper examines how redshift-dependent corrections for the age of Type Ia supernova progenitors affect measurements of the deceleration parameter q0 in the Pantheon+ catalogue. Prior tomographic analysis had found a strong local dipole in q0 aligned with bulk flow but only a small monopole at distances beyond a few hundred Mpc. After the age corrections the monopole moves to positive values, corresponding to deceleration on cosmological scales, while the dipole component stays essentially the same. A sympathetic reader would care because this suggests the apparent cosmic acceleration inferred from supernovae may arise from uncorrected evolutionary effects rather than from dark energy.

Core claim

Our recent redshift tomographic analysis showed that locally q0 has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying redshift-dependent corrections for progenitor age to the Pantheon+ catalogue, we find that this shifts the monopole component of q0 to positive values (i.e. deceleration), while leaving the local dipole component essentially unchanged.

What carries the argument

Redshift-dependent progenitor age corrections applied to Pantheon+ Type Ia supernovae within a tomographic decomposition of q0 into monopole and dipole components.

If this is right

  • The monopole component of q0 becomes positive on scales exceeding a few hundred Mpc.
  • The local dipole anisotropy in q0 remains largely unchanged and aligned with the bulk flow.
  • Cosmographic inferences of cosmic acceleration from supernovae depend on the treatment of progenitor age effects.
  • Standard interpretations of the Pantheon+ data for dark energy models are altered by these corrections.

Where Pith is reading between the lines

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

  • If the corrections hold, the need for a dominant dark energy component at late times would be reduced or eliminated in supernova-based analyses.
  • This result could be tested by applying the same age corrections to other supernova compilations such as those from DES or LSST.
  • It raises the possibility that other distance indicators may also require similar evolutionary adjustments to reconcile local and global expansion measures.

Load-bearing premise

The redshift-dependent progenitor age corrections accurately capture luminosity evolution without introducing new systematic biases.

What would settle it

A measurement showing that the monopole of q0 remains near zero or negative after the same age corrections are applied to an independent supernova sample or after direct empirical checks of luminosity versus progenitor age.

Figures

Figures reproduced from arXiv: 2606.09650 by Animesh Sah (TIFR Mumbai), Mohamed Rameez (TIFR Mumbai), Subir Sarkar (University of Oxford).

Figure 1
Figure 1. Figure 1: Apparent B-band magnitude as a function of heliocentric redshift for the Pantheon+ SNe Ia catalogue. The black points show the baseline magnitudes (𝑚B) without progenitor age correction, while the red points (𝑚∗ B ) are corrected for progenitor age following Son et al. (2025). with and without progenitor age bias corrections. While the statis￾tical significance of the dipole remains unchanged, the monopole… view at source ↗
Figure 2
Figure 2. Figure 2: Contours at 1, 2, 3, 4, 5, 6 and 7𝜎 for 𝑞m and 𝒒d in the heliocentric, CMB, Hubble diagram (CMB frame with peculiar velocity corrections) and Local Group frames, for Pantheon+ SNe Ia with a redshift cut: 0.00937 < 𝑧 < 0.8. The black cross is the best-fit with the progenitor age correction, while the red circle is the best-fit without such correction reported earlier (Sah et al. 2025). The magenta star deno… view at source ↗
Figure 3
Figure 3. Figure 3: The monopole 𝑞m of the deceleration parameter for Pantheon+ SNe Ia with progressively higher cuts in redshift (𝑧 > 𝑧min): in the heliocentric, CMB, Hubble diagram (CMB with peculiar velocity corrections) and Local Group frames. Error bars indicate 1𝜎 uncertainties obtained using Wilk’s theorem. Black and red points indicate the measurements with and without age-bias corrections. The dashed horizontal line … view at source ↗
Figure 4
Figure 4. Figure 4: The local dipole 𝒒d in the deceleration parameter evaluated in 17 shells containing around 100 SNe Ia each, plotted against their median red￾shift. The parameterisation is scale-independent, i.e. 𝑞0 = 𝑞m + 𝒒d · 𝑛ˆ within each shell. Open circles and stars denote results without and with progenitor age–dependent luminosity evolution corrections. Analyses are performed in the heliocentric, CMB, Hubble diagra… view at source ↗
read the original abstract

We examine the impact of progenitor age-dependent luminosity evolution of Type Ia supernovae on a cosmographic measurement of the deceleration parameter $q_0$. Our recent redshift tomographic analysis showed that locally $q_0$ has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying redshift-dependent corrections for progenitor age to the Pantheon+ catalogue, we find that this shifts the monopole component of $q_0$ to positive values (i.e. deceleration), while leaving the local dipole component essentially unchanged.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript applies redshift-dependent corrections for progenitor age luminosity evolution to the Pantheon+ Type Ia supernova catalogue. Building on the authors' prior redshift tomographic analysis, it reports that these corrections shift the monopole component of the deceleration parameter q0 to positive values (indicating deceleration at large distances), while the local dipole anisotropy aligned with the bulk flow remains essentially unchanged.

Significance. If the age corrections prove robust and independent of the tomographic fitting choices, the result would challenge the standard interpretation of SNIa data as evidence for cosmic acceleration, suggesting instead that apparent acceleration arises from unaccounted progenitor evolution. The analysis benefits from the large Pantheon+ sample and the tomographic decomposition approach, which allows separation of monopole and dipole components.

major comments (2)
  1. [Methods] The central claim that the monopole shifts to positive q0 rests on the redshift-dependent age corrections accurately isolating luminosity evolution without introducing distance-dependent biases or correlations with Pantheon+ selection effects. The manuscript should provide the explicit functional form of the correction, its calibration sample, and a test showing that the correction is uncorrelated with the distance modulus residuals used in the q0 fit.
  2. [Results] The reported shift is defined relative to the monopole and dipole values obtained in the authors' prior tomographic analysis. A re-derivation of the full tomographic decomposition on the age-corrected magnitudes is needed to demonstrate that the monopole change is not an artifact of the inherited fitting assumptions or parameter choices from that earlier work.
minor comments (2)
  1. [Abstract] The abstract would benefit from a brief quantitative statement of the magnitude of the monopole shift and its uncertainty.
  2. Notation for q0 components (monopole vs. dipole) should be defined consistently in the text and any equations.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive review and the recommendation for major revision. We address each major comment below and indicate the revisions that will be incorporated into the manuscript.

read point-by-point responses
  1. Referee: [Methods] The central claim that the monopole shifts to positive q0 rests on the redshift-dependent age corrections accurately isolating luminosity evolution without introducing distance-dependent biases or correlations with Pantheon+ selection effects. The manuscript should provide the explicit functional form of the correction, its calibration sample, and a test showing that the correction is uncorrelated with the distance modulus residuals used in the q0 fit.

    Authors: We agree that further documentation of the age correction procedure is needed to substantiate the central claim. In the revised manuscript we will explicitly state the functional form of the redshift-dependent progenitor age correction, identify the calibration sample, and include a quantitative test confirming that the correction shows no significant correlation with the distance modulus residuals entering the q0 fit. These additions will directly address concerns about possible distance-dependent biases or selection-effect correlations. revision: yes

  2. Referee: [Results] The reported shift is defined relative to the monopole and dipole values obtained in the authors' prior tomographic analysis. A re-derivation of the full tomographic decomposition on the age-corrected magnitudes is needed to demonstrate that the monopole change is not an artifact of the inherited fitting assumptions or parameter choices from that earlier work.

    Authors: We acknowledge that re-deriving the tomographic decomposition directly on the age-corrected Pantheon+ magnitudes would eliminate any ambiguity arising from the use of previously published monopole and dipole values. We will carry out this full re-derivation in the revised manuscript, thereby confirming that the reported shift to positive monopole q0 is independent of the fitting assumptions inherited from the earlier analysis. revision: yes

Circularity Check

1 steps flagged

Monopole shift in q0 defined relative to authors' prior self-cited tomographic decomposition

specific steps
  1. self citation load bearing [Abstract]
    "Our recent redshift tomographic analysis showed that locally q0 has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying redshift-dependent corrections for progenitor age to the Pantheon+ catalogue, we find that this shifts the monopole component of q0 to positive values (i.e. deceleration), while leaving the local dipole component essentially unchanged."

    The claimed shift is defined relative to the monopole and dipole values from the authors' prior tomographic analysis (same team). The new conclusion therefore inherits the fitting choices, data handling, and decomposition assumptions of that earlier self-cited work; the result is not independently derived from the age corrections alone.

full rationale

The paper's central result—that age corrections shift the q0 monopole to positive values while the dipole is unchanged—is explicitly measured against the monopole/dipole values obtained in the authors' own recent redshift tomographic analysis. This makes the load-bearing baseline a self-citation whose assumptions (tomographic binning, fitting procedure, Pantheon+ handling) are inherited without re-derivation or external check in the present work. The age-correction step itself is new and not shown to reduce to the prior result by construction, so the circularity is partial rather than total. No self-definitional equations, fitted-input predictions, or ansatz smuggling are exhibited in the provided text.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract supplies no explicit free parameters, axioms, or invented entities; the analysis rests on an unspecified age-luminosity correction model and on the authors' prior tomographic decomposition whose details are not provided here.

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