Can coupled thawing quintessence reproduce DESI DR2? A test with two potentials
Abstract
DESI DR2 favours dark energy whose equation of state evolves crossing w=−1 in the past. Coupled quintessence can produce such an apparent phantom crossing without a phantom field, since a coupled dark sector analysed under the assumption of separate conservation yields an effective equation of state below −1. We test whether this mechanism can reproduce the DESI result, using two thawing potentials, a cosine and a double-exponential hilltop, confronted with DESI DR2 BAO, Planck PR4 and three supernova compilations. Both models improve on ΛCDM by Δχ2 = 5--$15$, recovering $64−−92\%$ of the improvement achieved by w0waCDM. They track the w0waCDM equation of state at z≲0.4 but cross the phantom divide later, near z≃1 rather than z≃0.4--$0.5$. The coupling is bounded at |β|<0.073 (95%), and the two potentials agree on it to within 0.15σ. They differ instead in the equation of state they can reach: the cosine comes closer to the evolution preferred by DESI and is weakly preferred by the fit. The coupling posterior is bimodal, with modes at β≃±0.05; only the negative mode produces the crossing, and it is the higher of the two in every analysis. In conclusion, the data favour the coupled quintessence phantom crossing but do not yet require it.
Related
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BibTeX
@misc{babu2026coupled,
title = {{Can coupled thawing quintessence reproduce DESI DR2? A test with two potentials}},
author = {Jhananii Yuvaraj Babu and Luca Amendola},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.23497},
eprint = {2610.23497},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.23497},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Can coupled thawing quintessence reproduce DESI DR2? A test with two potentials
AU - Jhananii Yuvaraj Babu
AU - Luca Amendola
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.23497
UR - https://arxiv.org/abs/2610.23497
AB - DESI DR2 favours dark energy whose equation of state evolves crossing w=−1 in the past. Coupled quintessence can produce such an apparent phantom crossing without a phantom field, since a coupled dark sector analysed under the assumption of separate conservation yields an effective equation of state below −1. We test whether this mechanism can reproduce the DESI result, using two thawing potentials, a cosine and a double-exponential hilltop, confronted with DESI DR2 BAO, Planck PR4 and three supernova compilations. Both models improve on ΛCDM by Δχ^2 = 5--$15$, recovering $64−−92\%$ of the improvement achieved by w_0w_aCDM. They track the w_0w_aCDM equation of state at z≲0.4 but cross the phantom divide later, near z≃1 rather than z≃0.4--$0.5$. The coupling is bounded at |β|<0.073 (95%), and the two potentials agree on it to within 0.15σ. They differ instead in the equation of state they can reach: the cosine comes closer to the evolution preferred by DESI and is weakly preferred by the fit. The coupling posterior is bimodal, with modes at β≃±0.05; only the negative mode produces the crossing, and it is the higher of the two in every analysis. In conclusion, the data favour the coupled quintessence phantom crossing but do not yet require it.
ER -