Early Dark Energy Crowds Out Interacting Dark Energy
Abstract
We investigate whether interacting dark energy can provide additional relief to the Hubble tension once early dark energy (EDE) is present. Considering a cosmology containing EDE, an independent late-time dark energy fluid with an equation of state fixed at w≃−1 interacting with cold dark matter, and a cosmological constant, we find that the data strongly drive the model toward the non-interacting limit. The best fit effectively reduces to the standard EDE cosmology, where a non-zero EDE component provides most of the required increase in H0, leaving little statistical gain for the interaction. Although energy transfer from dark matter to dark energy can raise H0 further, this limited gain is rapidly outweighed by the deterioration of the fit to low-redshift observations. In particular, since the CMB tightly constrains the early-time physical matter density, any additional energy transfer requires a lower present-day matter abundance. Such low values are strongly disfavored by Type Ia supernovae. We show that this limitation becomes particularly severe once EDE has already raised H0 and that the same mechanism extends to a broad class of post-recombination interactions. Allowing a dynamical dark energy equation of state of the Chevallier-Polarski-Linder form does not alter our conclusions.
Related
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BibTeX
@misc{giare2026early,
title = {{Early Dark Energy Crowds Out Interacting Dark Energy}},
author = {William Giarè and Jeremy Sakstein},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37836},
eprint = {2610.37836},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37836},
}
RIS
TY - UNPB
TI - Early Dark Energy Crowds Out Interacting Dark Energy
AU - William Giarè
AU - Jeremy Sakstein
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37836
UR - https://arxiv.org/abs/2610.37836
AB - We investigate whether interacting dark energy can provide additional relief to the Hubble tension once early dark energy (EDE) is present. Considering a cosmology containing EDE, an independent late-time dark energy fluid with an equation of state fixed at w≃−1 interacting with cold dark matter, and a cosmological constant, we find that the data strongly drive the model toward the non-interacting limit. The best fit effectively reduces to the standard EDE cosmology, where a non-zero EDE component provides most of the required increase in H_0, leaving little statistical gain for the interaction. Although energy transfer from dark matter to dark energy can raise H_0 further, this limited gain is rapidly outweighed by the deterioration of the fit to low-redshift observations. In particular, since the CMB tightly constrains the early-time physical matter density, any additional energy transfer requires a lower present-day matter abundance. Such low values are strongly disfavored by Type Ia supernovae. We show that this limitation becomes particularly severe once EDE has already raised H_0 and that the same mechanism extends to a broad class of post-recombination interactions. Allowing a dynamical dark energy equation of state of the Chevallier-Polarski-Linder form does not alter our conclusions.
ER -