Beyond CPL: Evidence for dynamical dark energy in three-parameter models
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| Format: | Preprint |
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2025
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| author | Alam, Sonej Hossain, Md. Wali |
| author_facet | Alam, Sonej Hossain, Md. Wali |
| contents | We introduce two three-parameter extensions of the minimal Akhtar-Hossain (mAH) dark energy parametrization, termed modified minimal AH (MmAH1 and MmAH2), which provide a smooth and bounded evolution of the dark energy equation of state while retaining $Λ$CDM as a limiting case. Using a joint analysis of the CMB compressed likelihood, DESI DR2 BAO, $H(z)$, redshift space distortions, and three SNeIa samples (PantheonPlus, Union3, and DESY5), we compare these models with $Λ$CDM, $w$CDM, mAH, CPL, and the three-parameter CPL-$w_{\rm b}$ extension. The standard cosmological parameters remain stable across all models, while CPL, MmAH1 and MmAH2 parametrizations yield modest but consistent improvements in fit ($Δχ^2\simeq-6$ to $-12$ for PantheonPlus and Union3, and $\simeq-38$ for DESY5). Statistical consistency with $Λ$CDM, quantified via the Mahalanobis distance in one, two, and three dimensional parameter subspaces, reveals mild to moderate deviations, $\sim2$--$2.5σ$ for $+$PantheonPlus, $2$--$3σ$ for $+$Union3, and up to $4$--$5σ$ for $+$DESY5 combination, depending on model complexity. Among all extensions CPL, MmAH1 and MmAH2 provide the most stable and physically coherent representations of dynamical dark energy, maintaining moderate tensions with $Λ$CDM and well behaved parameter correlations. Overall, these results indicate consistent evidence for departures from $Λ$CDM. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_03779 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Beyond CPL: Evidence for dynamical dark energy in three-parameter models Alam, Sonej Hossain, Md. Wali Cosmology and Nongalactic Astrophysics We introduce two three-parameter extensions of the minimal Akhtar-Hossain (mAH) dark energy parametrization, termed modified minimal AH (MmAH1 and MmAH2), which provide a smooth and bounded evolution of the dark energy equation of state while retaining $Λ$CDM as a limiting case. Using a joint analysis of the CMB compressed likelihood, DESI DR2 BAO, $H(z)$, redshift space distortions, and three SNeIa samples (PantheonPlus, Union3, and DESY5), we compare these models with $Λ$CDM, $w$CDM, mAH, CPL, and the three-parameter CPL-$w_{\rm b}$ extension. The standard cosmological parameters remain stable across all models, while CPL, MmAH1 and MmAH2 parametrizations yield modest but consistent improvements in fit ($Δχ^2\simeq-6$ to $-12$ for PantheonPlus and Union3, and $\simeq-38$ for DESY5). Statistical consistency with $Λ$CDM, quantified via the Mahalanobis distance in one, two, and three dimensional parameter subspaces, reveals mild to moderate deviations, $\sim2$--$2.5σ$ for $+$PantheonPlus, $2$--$3σ$ for $+$Union3, and up to $4$--$5σ$ for $+$DESY5 combination, depending on model complexity. Among all extensions CPL, MmAH1 and MmAH2 provide the most stable and physically coherent representations of dynamical dark energy, maintaining moderate tensions with $Λ$CDM and well behaved parameter correlations. Overall, these results indicate consistent evidence for departures from $Λ$CDM. |
| title | Beyond CPL: Evidence for dynamical dark energy in three-parameter models |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2510.03779 |