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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 ΛCDM parameter Ωₘ from the w₀ wₐCDM cosmologies advocated by the DESI collaboration. We identify i) a mild increasing Ωₘ trend at high redshift and ii) a sharp departure from ΛCDM 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 Ωₘ at the same effective redshift. This ``Ωₘ tension'' most likely points to unexplored systematics. In general, any bona fide DDE signal should be confirmed independently across observables, so the DDE claims are premature.
Colgáin et al. (Tue,) studied this question.