Testing cosmic anisotropy with Pade approximation and Pantheon+ sample
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arXiv
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2024
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| author | Hu, Jianping Hu, Jian Jia, Xuandong Gao, Baoquan Wang, Fayin |
| author_facet | Hu, Jianping Hu, Jian Jia, Xuandong Gao, Baoquan Wang, Fayin |
| contents | Cosmography can be used to constrain the kinematics of universe in a model-independent way. In this work, we attempted to combine the Pad$\rm \acute{e}$ approximations with the latest Pantheon+ sample for testing cosmological principle. Based on the Pad$\rm \acute{e}$ approximations, we first gave the cosmographic constraints on the different order polynomials including third-order (Pad$\rm \acute{e}$$_{(2,1)}$), fourth-order (Pad$\rm \acute{e}$$_{(2,2)}$) and fifth-order (Pad$\rm \acute{e}$$_{(3,2)}$). Based on the Pad$\rm \acute{e}$$_{(2,1)}$ ($j_{0}$ = 1) polynomial and hemisphere comparison (HC) method, we tested the cosmological principle and found the preferred directions of cosmic anisotropy, such as (l, b) = (304.6$^{\circ}$$_{-37.4}^{+51.4}$, $-$18.7$^{\circ}$$_{-20.3}^{+14.7}$) and (311.1$^{\circ}$$_{-8.4}^{+17.4}$, $-$17.53$^{\circ}$$_{-7.7}^{+7.8}$) for $q_{0}$ and $H_{0}$, respectively. These two directions are consistent with each other in $1σ$ confidence level, but the corresponding results of statistical isotropy analyses including Isotropy and Isotropy with real positions (RP) are quite different. The statistical significance of $H_{0}$ are stronger than that of $q_{0}$, i.e., 4.75$σ$ and 4.39$σ$ for the Isotropy and Isotropy with RP respectively. Reanalysis with fixed $q_{0} = -0.55$ (corresponds to $Ω_{m}$ = 0.30) gives similar results. Overall, our model-independent results provide clear indications for a possible cosmic anisotropy, which must be taken seriously. Further test is needed to better understand this signal. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2406_14827 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Testing cosmic anisotropy with Pade approximation and Pantheon+ sample Hu, Jianping Hu, Jian Jia, Xuandong Gao, Baoquan Wang, Fayin Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology Cosmography can be used to constrain the kinematics of universe in a model-independent way. In this work, we attempted to combine the Pad$\rm \acute{e}$ approximations with the latest Pantheon+ sample for testing cosmological principle. Based on the Pad$\rm \acute{e}$ approximations, we first gave the cosmographic constraints on the different order polynomials including third-order (Pad$\rm \acute{e}$$_{(2,1)}$), fourth-order (Pad$\rm \acute{e}$$_{(2,2)}$) and fifth-order (Pad$\rm \acute{e}$$_{(3,2)}$). Based on the Pad$\rm \acute{e}$$_{(2,1)}$ ($j_{0}$ = 1) polynomial and hemisphere comparison (HC) method, we tested the cosmological principle and found the preferred directions of cosmic anisotropy, such as (l, b) = (304.6$^{\circ}$$_{-37.4}^{+51.4}$, $-$18.7$^{\circ}$$_{-20.3}^{+14.7}$) and (311.1$^{\circ}$$_{-8.4}^{+17.4}$, $-$17.53$^{\circ}$$_{-7.7}^{+7.8}$) for $q_{0}$ and $H_{0}$, respectively. These two directions are consistent with each other in $1σ$ confidence level, but the corresponding results of statistical isotropy analyses including Isotropy and Isotropy with real positions (RP) are quite different. The statistical significance of $H_{0}$ are stronger than that of $q_{0}$, i.e., 4.75$σ$ and 4.39$σ$ for the Isotropy and Isotropy with RP respectively. Reanalysis with fixed $q_{0} = -0.55$ (corresponds to $Ω_{m}$ = 0.30) gives similar results. Overall, our model-independent results provide clear indications for a possible cosmic anisotropy, which must be taken seriously. Further test is needed to better understand this signal. |
| title | Testing cosmic anisotropy with Pade approximation and Pantheon+ sample |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2406.14827 |