The prior dependence of the DESI results

Abstract

In this short contribution, we explore the prior dependence of the recent DESI results, according to which a Bayesian comparison of $\Lambda$CDM with $w_0{w}_a$CDM cosmologies favors dynamical dark energy. It is a simple exercise to show that extending the prior lower bound of the dark energy parameters tilts the preference in favor of $\Lambda$CDM. Adopting the PantheonPlus supernovae catalog, for instance, a shift of the lower bound for $w_0,w_a$ from $-3$ to beyond $-4.6$ and $-5$, respectively, is sufficient to favor $\Lambda$CDM. This calls for caution when interpreting DESI results in the Bayesian context.

4 pages; v2: added some elaborate calculation

Cited by in corpus (2)

• Robust Preference for Dynamical Dark Energy in DESI BAO and SN Measurements
• The Impact of ${\Omega }_{m0}$ Prior Bias on Cosmological Parameter Estimation: Reconciling DESI DR2 BAO and Pantheon+ SNe Data Combination Results