Examining the Linear and Quadratic Dark Energy Parameterizations with DESI DR2 via AIC and BIC Selection
Abstract
We examine whether or not the current observational preference for a dynamical dark energy(DE), as reported by DESI, is an artifact of the chosen functional form of dark energy equation of state (EoS) parameter w(z) by considering a higher-order quadratic extension in EoS. We explore three distinct parameterizations of the DE models: the two-parameter (linear) Chevallier-Polarski-Linder (CPL) and Wang models, alongside a three-parameter parabolic (quadratic) formulation. Using a joint dataset of CMB measurements from Planck and ACT DR6, baryon acoustic oscillations of DESI DR2, and Type Ia supernovae from Pantheon+ and DES-SN5YR, we constrain the model parameters and observe a maximum frequentist preference of up to ∼ 4σ for these dynamical models. Specifically, the joint CMB + DESI + DES-SN5YR combination yields a substantial improvement in fit over ΛCDM, with Δχ2min values of −20.5, −19.4, and −21.7 for CPL, Wang, and Parabolic models, respectively. In addition, the Akaike Information Criterion (AIC) provides weak to no evidence for ΛCDM, consistently favoring the dynamical DE models instead. On the other hand, the Bayesian Information Criterion (BIC) imposes a heavy penalty on all the three models, reflecting its high sensitivity to dataset size and model complexity. We find at best a mild support for CPL and Wang models but the Parabolic model is strongly disfavored (ΔBIC ∼ +6.4 to +15.6). Furthermore, due to its expanded parameter space, the Parabolic model exhibits a significant reduction in the Figure of Merit (FoM) compared to the two-parameter counterparts, demonstrating that the current cosmological datasets do not yet justify an introduction of the higher-order DE models. So, as a result, the two-parameter descriptions of w(z) remain the optimal choice for testing the dynamical DE signatures.
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BibTeX
@misc{mangang2026examining,
title = {{Examining the Linear and Quadratic Dark Energy Parameterizations with DESI DR2 via AIC and BIC Selection}},
author = {Laiphangbam Khumaba Mangang and Yumnam Prakash Singh and N. Chandrachani Devi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.02910},
eprint = {2609.02910},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.02910},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Examining the Linear and Quadratic Dark Energy Parameterizations with DESI DR2 via AIC and BIC Selection
AU - Laiphangbam Khumaba Mangang
AU - Yumnam Prakash Singh
AU - N. Chandrachani Devi
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.02910
UR - https://arxiv.org/abs/2609.02910
AB - We examine whether or not the current observational preference for a dynamical dark energy(DE), as reported by DESI, is an artifact of the chosen functional form of dark energy equation of state (EoS) parameter w(z) by considering a higher-order quadratic extension in EoS. We explore three distinct parameterizations of the DE models: the two-parameter (linear) Chevallier-Polarski-Linder (CPL) and Wang models, alongside a three-parameter parabolic (quadratic) formulation. Using a joint dataset of CMB measurements from Planck and ACT DR6, baryon acoustic oscillations of DESI DR2, and Type Ia supernovae from Pantheon+ and DES-SN5YR, we constrain the model parameters and observe a maximum frequentist preference of up to ∼ 4σ for these dynamical models. Specifically, the joint CMB + DESI + DES-SN5YR combination yields a substantial improvement in fit over ΛCDM, with Δχ^2_min values of −20.5, −19.4, and −21.7 for CPL, Wang, and Parabolic models, respectively. In addition, the Akaike Information Criterion (AIC) provides weak to no evidence for ΛCDM, consistently favoring the dynamical DE models instead. On the other hand, the Bayesian Information Criterion (BIC) imposes a heavy penalty on all the three models, reflecting its high sensitivity to dataset size and model complexity. We find at best a mild support for CPL and Wang models but the Parabolic model is strongly disfavored (ΔBIC ∼ +6.4 to +15.6). Furthermore, due to its expanded parameter space, the Parabolic model exhibits a significant reduction in the Figure of Merit (FoM) compared to the two-parameter counterparts, demonstrating that the current cosmological datasets do not yet justify an introduction of the higher-order DE models. So, as a result, the two-parameter descriptions of w(z) remain the optimal choice for testing the dynamical DE signatures.
ER -