Are evolving dark energy hints driven by supernova systematics?
This text mentions work from 2024 on. Those parts were partly written without a live literature search and have not been checked by an editor yet.
In plain words
Exploding stars called type Ia supernovae serve as distance markers, and the dark energy hint depends on which supernova catalog is used. Small calibration errors between nearby and distant supernovae could fake the signal.
Precise statement
The DESI DR2 preference for $w0-wa$ ranges from about $2.8\text{ to }4.2\sigma$ across Pantheon+, Union3 and DES-Y5, and the 2025 DES reanalysis (Dovekie) lowered the DES value. Determine whether a distance-modulus offset of order $0.04\,\mathrm{mag}$ between low-redshift ($z < 0.1$) and high-redshift supernovae, from photometric calibration, selection, or host-galaxy dust and age evolution, accounts for the signal. Answer: identification of such a systematic or a demonstration that all such offsets are below $0.01\,\mathrm{mag}$.
What would settle it
A single-survey supernova sample spanning $0 < z < 1$ on one photometric system, cross-checked against BAO-only and CMB-only fits.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
The 2025 DES-Dovekie recalibration reduced the preference from 4.2 to about $3.2\sigma$ with DESI DR2 and CMB.
Parent problems
- Special case of Is the dark energy density constant in time? · open · from revision 1
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