Cosmology and Nongalactic Astrophysics2026-01-13v1General Relativity and Quantum CosmologyHigh Energy Physics - PhenomenologyHigh Energy Physics - Theory
Recent DESI baryon acoustic oscillation data reveal deviations from ΛCDM cosmology, conventionally attributed to dynamical dark energy (DE). We demonstrate that these deviations are equally, if not better, explained by interactions between dark matter and dark energy (IDE), without requiring a time-varying DE equation of state. Using a unified framework, we analyze two IDE models -- coupled quintessence and coupled fluid -- against the latest CMB (Planck, ACT, SPT), DESI BAO, and SN (including DES-Dovekie recalibrated) data. Both IDE scenarios show robust evidence for non-vanishing interactions at the 3-5σ level, with marginalized constraints significantly deviating from the ΛCDM limit. This preference persists even under DES-Dovekie SN recalibration, which weakens dynamical DE evidence. Crucially, for the same number of free parameters, IDE models provide fits to low- and high-redshift data that match or exceed the performance of the CPL dynamical DE parametrization. Our results establish IDE as a physically motivated alternative to dynamical DE, highlighting the necessity of future cosmological perturbation measurements (e.g., weak lensing, galaxy clustering) to distinguish between these paradigms.
@article{arxiv.2601.07361,
title = {Strong Evidence for Dark Sector Interactions},
author = {Tian-Nuo Li and William Giarè and Guo-Hong Du and Yun-He Li and Eleonora Di Valentino and Jing-Fei Zhang and Xin Zhang},
journal= {arXiv preprint arXiv:2601.07361},
year = {2026}
}