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arXiv · 2412.12905

DESI and SNe: Dynamical Dark Energy, $Ω_m$ Tension or Systematics?

Eoin Ó Colgáin·M. M. Sheikh-Jabbari
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Abstract

Dark Energy Spectroscopic Instrument (DESI) observations, when combined with Cosmic Microwave Background (CMB) and Type Ia supernovae (SNe), have led to statistically significant dynamical dark energy (DDE) claims. In this letter we reconstruct the $Λ$CDM parameter $Ω_m$ from the $w_0 w_a$CDM cosmologies advocated by the DESI collaboration. We identify i) a mild increasing $Ω_m$ trend at high redshift and ii) a sharp departure from $Λ$CDM at low redshift. The latter, which is statistically significant, is driven by SNe that are $1.9 σ- 2.5 σ$ discrepant with DESI full-shape galaxy clustering in overlapping redshift ranges. We identify a low redshift subsample of the Dark Energy Survey (DES) SNe sample that is discrepant with DESI at $3.4 σ$ despite both observables probing the same effective redshift. SNe and BAO/full-shape modeling should not disagree on $Ω_m$ at the same effective redshift. This ``$Ω_m$ tension'' most likely points to unexplored systematics. In general, any \textit{bona fide} DDE signal should be confirmed independently across observables, so the DDE claims are premature.

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Eoin Ó Colgáin, M. M. Sheikh-Jabbari. 2025-01-25. DESI and SNe: Dynamical Dark Energy, $Ω_m$ Tension or Systematics?. https://arxiv.org/abs/2412.12905

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