Pressure Parametrization of Dark Energy: First and Second-Order Constraints with Latest Cosmological Data
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| Format: | Preprint |
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2025
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| _version_ | 1866915502924759040 |
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| author | Cheng, Hanyu Di Valentino, Eleonora Escamilla, Luis A. Sen, Anjan A. Visinelli, Luca |
| author_facet | Cheng, Hanyu Di Valentino, Eleonora Escamilla, Luis A. Sen, Anjan A. Visinelli, Luca |
| contents | We explore an extension of the $Λ$CDM model in which the pressure $p$ of the dark energy (DE) fluid evolves with the expansion of the Universe, expressed as a function of the scale factor $a$. The corresponding energy density $ρ$ is derived from the continuity equation, resulting in a dynamical equation-of-state parameter $w \equiv p/ρ$ during the late-time expansion of the Universe. The pressure is modeled using a Taylor expansion around the present epoch ($a = 1$), introducing deviations from a cosmological constant within the dynamical dark energy (DDE) framework. At first order, a single new parameter $Ω_1$ captures linear deviations, while a second-order parameter, $Ω_2$, accounts for quadratic evolution in the pressure. We constrain the first- and second-order DDE models using multiple observational datasets and compare their performance against $Λ$CDM and the CPL parameterization. A joint analysis of Planck CMB, DESI, and DESY5 data yields the strongest evidence for DDE, with a $2.7σ$ deviation in the first-order model and over $4σ$ in the second-order model, providing strong statistical support for a departure from a cosmological constant. The reconstructed DE evolution in the second-order case reveals a distinctive non-monotonic behavior in both energy density and $w_{\rm DE}(a)$, including clear phantom-crossing phenomena. Notably, the late-time evolution of $w_{\rm DE}(a)$ remains consistent across datasets and shows strong agreement with the CPL parameterization, underscoring the robustness of the pressure-based approach. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_02932 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Pressure Parametrization of Dark Energy: First and Second-Order Constraints with Latest Cosmological Data Cheng, Hanyu Di Valentino, Eleonora Escamilla, Luis A. Sen, Anjan A. Visinelli, Luca Cosmology and Nongalactic Astrophysics We explore an extension of the $Λ$CDM model in which the pressure $p$ of the dark energy (DE) fluid evolves with the expansion of the Universe, expressed as a function of the scale factor $a$. The corresponding energy density $ρ$ is derived from the continuity equation, resulting in a dynamical equation-of-state parameter $w \equiv p/ρ$ during the late-time expansion of the Universe. The pressure is modeled using a Taylor expansion around the present epoch ($a = 1$), introducing deviations from a cosmological constant within the dynamical dark energy (DDE) framework. At first order, a single new parameter $Ω_1$ captures linear deviations, while a second-order parameter, $Ω_2$, accounts for quadratic evolution in the pressure. We constrain the first- and second-order DDE models using multiple observational datasets and compare their performance against $Λ$CDM and the CPL parameterization. A joint analysis of Planck CMB, DESI, and DESY5 data yields the strongest evidence for DDE, with a $2.7σ$ deviation in the first-order model and over $4σ$ in the second-order model, providing strong statistical support for a departure from a cosmological constant. The reconstructed DE evolution in the second-order case reveals a distinctive non-monotonic behavior in both energy density and $w_{\rm DE}(a)$, including clear phantom-crossing phenomena. Notably, the late-time evolution of $w_{\rm DE}(a)$ remains consistent across datasets and shows strong agreement with the CPL parameterization, underscoring the robustness of the pressure-based approach. |
| title | Pressure Parametrization of Dark Energy: First and Second-Order Constraints with Latest Cosmological Data |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2505.02932 |