Sensitivity of calibration-free DESI DR2 BAO--supernova constraints to a distance-duality tilt
Abstract
Recent measurements from DESI baryon acoustic oscillations (BAO) have reported a moderate preference for dynamical dark energy, challenging the ΛCDM paradigm. Nonetheless, such a trend could reflect a tension between the shape and the offset of the Hubble diagrams predicted by current BAO and Type Ia supernovae (SN) data, which may underpin a possible breakdown of the cosmic distance duality relation linking luminosity distances DL and angular-diameter distances DA. We explore this possibility by parametrizing deviations from this relation as η(z)≡ DL/[(1+z)2DA]=α(1+z)ε, and investigate how the preference for a Chevallier-Polarski-Linder (CPL) dynamical dark energy is modified once ε≠0 is allowed. Using DESI DR2 and uncalibrated SN data (Pantheon+, DES-Dovekie, Union3, and Union3.1), we find that allowing ε to vary freely in both ΛCDM and CPL reduces the CPL preference with respect to ΛCDM by a larger amount than the addition of spatial curvature Ωk; only Union3.1 exhibits comparable reductions. We also find that the preference reduction is robust to alternative η(z) parametrizations, and that the η(z) constraints remain stable under the removal of BAO tracers or low-redshift cutoffs for Pantheon+, whereas the DES-Dovekie preference largely disappears once z<0.1 SN are removed. In a separate calibrated analysis, illustrative Planck sound-horizon and SH0ES absolute-magnitude priors give α≃0.942±0.014, quantifying the normalization mismatch under those assumptions. We also discuss photon-loss and varying-G interpretations: ordinary positive opacity cannot explain the negative central tilts ε found for a ΛCDM background, while local gravity tests strongly constrain the illustrative unscreened varying-G scenario.
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BibTeX
@misc{artola2026sensitivity,
title = {{Sensitivity of calibration-free DESI DR2 BAO--supernova constraints to a distance-duality tilt}},
author = {Mikel Artola and Stéphane Fay and Leandros Perivolaropoulos},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.16496},
eprint = {2610.16496},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.16496},
}
RIS
TY - UNPB
TI - Sensitivity of calibration-free DESI DR2 BAO--supernova constraints to a distance-duality tilt
AU - Mikel Artola
AU - Stéphane Fay
AU - Leandros Perivolaropoulos
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.16496
UR - https://arxiv.org/abs/2610.16496
AB - Recent measurements from DESI baryon acoustic oscillations (BAO) have reported a moderate preference for dynamical dark energy, challenging the ΛCDM paradigm. Nonetheless, such a trend could reflect a tension between the shape and the offset of the Hubble diagrams predicted by current BAO and Type Ia supernovae (SN) data, which may underpin a possible breakdown of the cosmic distance duality relation linking luminosity distances D_L and angular-diameter distances D_A. We explore this possibility by parametrizing deviations from this relation as η(z)≡ D_L/[(1+z)^2D_A]=α(1+z)^ε, and investigate how the preference for a Chevallier-Polarski-Linder (CPL) dynamical dark energy is modified once ε≠0 is allowed. Using DESI DR2 and uncalibrated SN data (Pantheon+, DES-Dovekie, Union3, and Union3.1), we find that allowing ε to vary freely in both ΛCDM and CPL reduces the CPL preference with respect to ΛCDM by a larger amount than the addition of spatial curvature Ω_k; only Union3.1 exhibits comparable reductions. We also find that the preference reduction is robust to alternative η(z) parametrizations, and that the η(z) constraints remain stable under the removal of BAO tracers or low-redshift cutoffs for Pantheon+, whereas the DES-Dovekie preference largely disappears once z<0.1 SN are removed. In a separate calibrated analysis, illustrative Planck sound-horizon and SH0ES absolute-magnitude priors give α≃0.942±0.014, quantifying the normalization mismatch under those assumptions. We also discuss photon-loss and varying-G interpretations: ordinary positive opacity cannot explain the negative central tilts ε found for a ΛCDM background, while local gravity tests strongly constrain the illustrative unscreened varying-G scenario.
ER -