Constraints on coupled dark energy in the DESI era
Phys. Rev. D 114, 043540 – Published 24 August, 2026
DOI: https://doi.org/10.1103/x8kc-zqzl
Abstract
We investigate the current viability of a well-known coupled dark energy scenario in which cold dark matter (CDM) interacts with a spin-0 dark energy component through a nontrivial field dependence of the dark matter (DM) mass. This ultralight scalar mediates a fifth force between DM particles, which can leave signatures on cosmological scales. We use state-of-the-art data on the cosmic microwave background from Planck’s camspec likelihood, baryon acoustic oscillations from the second DESI data release as well as the supernovae of Type Ia (SNIa) from DES-Dovekie. We perform the analysis considering both a flat potential and a Peebles-Ratra (PR) potential for the scalar field in order to assess the impact of the potential slope on the fitting performance of the model. While for a constant potential the scalar field dynamics is insensitive to the sign of the coupling parameter , the PR potential breaks the existing symmetry in the solutions at late times and could induce a difference at the phenomenological level between positive and negative values. We study for the first time if it is actually the case, finding no important asymmetry in the fitting results, essentially due to shifts in other parameters, which can lead to significant compensating effects. In the light of the aforesaid datasets, we find in all cases a peak at —less pronounced than reported in some recent works—excluding the no-coupling scenario at CL at most. The model is able to explain an effective crossing of the phantom divide, with the equation-of-state parameter lying within the bands of model-agnostic reconstructions, albeit with important differences in the shape of the central curves. Our results are very robust under changes in the SNIa sample used in the analysis and is not significantly altered when we replace a constant potential with the PR one, although the latter is crucial to produce the aforesaid crossing. In passing, we also provide constraints obtained with the PR potential in the uncoupled case.
