Interacting dark energy after DESI DR2: a challenge for $\Lambda$CDM paradigm?

Abstract

We investigate the scenario of interacting dark energy through a detailed confrontation with various observational datasets. We quantify the interaction in a general way, through the deviation from the standard scaling of the dark matter energy density. We use the cosmic microwave background (CMB) data from Planck 2018, data from Baryon Acoustic Oscillations (BAO) from the recently released DESI DR2, observational Hubble Data from Cosmic Chronometers (CC), and finally various Supernova Type Ia (SNIa) datasets (PantheonPlus, Union3 and DESY5). For the basic and simplest interacting model we find a mild preference of the interaction at slightly more than $1\sigma$ however still within $2\sigma$, and thus no strong evidence of interaction is found. However, comparison with $\Lambda$ cold dark matter ($\Lambda$CDM) scenario through $\Delta \chi^2_{\rm min}$, Akaike Information Criterion and Bayesian analysis, reveals a mixed picture, namely according to $\Delta \chi^2_{\rm min}$ the interaction is mildly favored by most of the datasets, while the remaining statistical measures are inclined toward $\Lambda$CDM.