$\mathbf{Ω_1Ω_2}$-$\mathbfΛ$CDM: A promising phenomenological extension of the standard model of cosmology
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| Format: | Preprint |
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2025
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| _version_ | 1866908840274952192 |
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| author | Kumar, Suresh |
| author_facet | Kumar, Suresh |
| contents | We investigate a phenomenological extension of the standard $Λ$CDM framework, the $Ω_1Ω_2$-$Λ$CDM model, in which the total energy density of the universe is expanded in powers of $1+z$. This parameterization recovers $Λ$CDM and introduces two additional terms, $Ω_1(1+z)$ and $Ω_2(1+z)^2$, in the dark energy sector alongside the cosmological constant, leading to a physically interpretable and observationally testable effective dark energy dynamics. Using Planck cosmic microwave background (CMB) data, we find that the model allows additional freedom in the late-time expansion history while preserving standard early-universe physics. When DESI baryon acoustic oscillation (BAO) data are included, the inferred Hubble constant is $H_0 = 69.74 \pm 0.77~\mathrm{km\;s^{-1}\;Mpc^{-1}}$ (68% CL), consistent with Tip of the Red Giant Branch (TRGB) measurements from the Carnegie--Chicago Hubble Program (CCHP). The reconstructed dark energy equation of state exhibits a smooth transition across the phantom divide followed by asymptotic de Sitter behavior, modifying late-time dynamics while maintaining standard early-time cosmology. Overall, controlled late-time deviations from $Λ$CDM improve cosmological concordance. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_19000 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | $\mathbf{Ω_1Ω_2}$-$\mathbfΛ$CDM: A promising phenomenological extension of the standard model of cosmology Kumar, Suresh Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We investigate a phenomenological extension of the standard $Λ$CDM framework, the $Ω_1Ω_2$-$Λ$CDM model, in which the total energy density of the universe is expanded in powers of $1+z$. This parameterization recovers $Λ$CDM and introduces two additional terms, $Ω_1(1+z)$ and $Ω_2(1+z)^2$, in the dark energy sector alongside the cosmological constant, leading to a physically interpretable and observationally testable effective dark energy dynamics. Using Planck cosmic microwave background (CMB) data, we find that the model allows additional freedom in the late-time expansion history while preserving standard early-universe physics. When DESI baryon acoustic oscillation (BAO) data are included, the inferred Hubble constant is $H_0 = 69.74 \pm 0.77~\mathrm{km\;s^{-1}\;Mpc^{-1}}$ (68% CL), consistent with Tip of the Red Giant Branch (TRGB) measurements from the Carnegie--Chicago Hubble Program (CCHP). The reconstructed dark energy equation of state exhibits a smooth transition across the phantom divide followed by asymptotic de Sitter behavior, modifying late-time dynamics while maintaining standard early-time cosmology. Overall, controlled late-time deviations from $Λ$CDM improve cosmological concordance. |
| title | $\mathbf{Ω_1Ω_2}$-$\mathbfΛ$CDM: A promising phenomenological extension of the standard model of cosmology |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2512.19000 |