Comments on the prior dependence of the DESI results

In this short contribution, we explore the prior dependence of the recent DESI results, according to which a Bayesian comparison of CDM with w₀wₐCDM 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 CDM. Adopting the PantheonPlus supernovae catalog, for instance, a shift of the lower bound for w₀, wₐ from -3 to beyond -4. 6 and -5, respectively, is sufficient to favor CDM. This calls for caution when interpreting DESI results in the Bayesian context.