Cosmological anatomy of interacting dark energy
Abstract
Interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE), have received significant renewed interest. However, little attention has been devoted to understanding their genuine cosmological signatures, with comparisons against ΛCDM often carried out at fixed cosmological parameters. Considering the widely studied model with energy exchange rate proportional to the DE density, we carry out a three-level sequence of comparisons, starting from the naïve fixed-parameter comparison, then compensating for shifts in θs and zeq, and then removing effects due to the modified background. We show that fixing θs and zeq leads to pre-recombination evolutions of the Weyl potential, photon monopole, and baryon velocity which are nearly identical to their ΛCDM counterparts, and hence virtually indistinguishable Cosmic Microwave Background (CMB) temperature power spectra. Comparing IDE to a non-interacting wCDM model with the same background, we find small scale-dependent signatures in CMB lensing. We find larger differences in the matter power spectrum, reflecting the different values of Ωm resulting from the different partition of the dark sector into DM and DE, with only percent-level differences remaining once we compare Ωm2Pm(k), indicating the importance of high-fidelity determinations of Ωm. Our controlled comparison strategy can be a powerful tool for a wide range of models beyond ΛCDM.
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BibTeX
@misc{sabogal2026cosmological,
title = {{Cosmological anatomy of interacting dark energy}},
author = {Miguel A. Sabogal and Sunny Vagnozzi and Eleonora Di Valentino},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18288},
eprint = {2609.18288},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18288},
}
RIS
TY - UNPB
TI - Cosmological anatomy of interacting dark energy
AU - Miguel A. Sabogal
AU - Sunny Vagnozzi
AU - Eleonora Di Valentino
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18288
UR - https://arxiv.org/abs/2609.18288
AB - Interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE), have received significant renewed interest. However, little attention has been devoted to understanding their genuine cosmological signatures, with comparisons against ΛCDM often carried out at fixed cosmological parameters. Considering the widely studied model with energy exchange rate proportional to the DE density, we carry out a three-level sequence of comparisons, starting from the naïve fixed-parameter comparison, then compensating for shifts in θ_s and z_eq, and then removing effects due to the modified background. We show that fixing θ_s and z_eq leads to pre-recombination evolutions of the Weyl potential, photon monopole, and baryon velocity which are nearly identical to their ΛCDM counterparts, and hence virtually indistinguishable Cosmic Microwave Background (CMB) temperature power spectra. Comparing IDE to a non-interacting wCDM model with the same background, we find small scale-dependent signatures in CMB lensing. We find larger differences in the matter power spectrum, reflecting the different values of Ω_m resulting from the different partition of the dark sector into DM and DE, with only percent-level differences remaining once we compare Ω_m^2P_m(k), indicating the importance of high-fidelity determinations of Ω_m. Our controlled comparison strategy can be a powerful tool for a wide range of models beyond ΛCDM.
ER -