Cosmic chronometers, Pantheon+ supernovae, and quasars favor coasting cosmologies over the flat $Λ$CDM model
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arXiv
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| Format: | Preprint |
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2024
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| author | Raffai, Peter Pataki, Adrienn Böttger, Rebeka L. Karsai, Alexandra Dálya, Gergely |
| author_facet | Raffai, Peter Pataki, Adrienn Böttger, Rebeka L. Karsai, Alexandra Dálya, Gergely |
| contents | We test and compare coasting cosmological models with curvature parameters ${k=\left\{ -1,0,+1 \right\}}$ in ${H_0^2 c^{-2}}$ units and the flat $Λ$CDM model by fitting them to cosmic chronometers (CC), the Pantheon+ sample of type Ia supernovae (SNe), and standardized quasars (QSOs). We used the \texttt{emcee} code for fitting CC data, a custom Markov Chain Monte Carlo implementation for SNe and QSOs, and Anderson-Darling tests for normality on normalized residuals for model comparison. Best-fit parameters are presented, constrained by data within redshift ranges $z\leq 2$ for CCs, $z\leq 2.3$ for SNe, and $z\leq 7.54$ for QSOs. Coasting models, particularly the flat coasting model, are generally favored over the flat $Λ$CDM model. The overfitting of the flat $Λ$CDM model to Pantheon+ SNe and the large intrinsic scatter in QSO data suggest a need to refine error estimates in these datasets. We also highlight the seemingly fine-tuned nature of either the CC data or $Ω_{\mathrm{m},0}$ in the flat $Λ$CDM model to an ${H_1=H_0}$ coincidence when fitting ${H(z)=H_1z+H_0}$, a natural feature of coasting models. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2412_15717 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Cosmic chronometers, Pantheon+ supernovae, and quasars favor coasting cosmologies over the flat $Λ$CDM model Raffai, Peter Pataki, Adrienn Böttger, Rebeka L. Karsai, Alexandra Dálya, Gergely Cosmology and Nongalactic Astrophysics We test and compare coasting cosmological models with curvature parameters ${k=\left\{ -1,0,+1 \right\}}$ in ${H_0^2 c^{-2}}$ units and the flat $Λ$CDM model by fitting them to cosmic chronometers (CC), the Pantheon+ sample of type Ia supernovae (SNe), and standardized quasars (QSOs). We used the \texttt{emcee} code for fitting CC data, a custom Markov Chain Monte Carlo implementation for SNe and QSOs, and Anderson-Darling tests for normality on normalized residuals for model comparison. Best-fit parameters are presented, constrained by data within redshift ranges $z\leq 2$ for CCs, $z\leq 2.3$ for SNe, and $z\leq 7.54$ for QSOs. Coasting models, particularly the flat coasting model, are generally favored over the flat $Λ$CDM model. The overfitting of the flat $Λ$CDM model to Pantheon+ SNe and the large intrinsic scatter in QSO data suggest a need to refine error estimates in these datasets. We also highlight the seemingly fine-tuned nature of either the CC data or $Ω_{\mathrm{m},0}$ in the flat $Λ$CDM model to an ${H_1=H_0}$ coincidence when fitting ${H(z)=H_1z+H_0}$, a natural feature of coasting models. |
| title | Cosmic chronometers, Pantheon+ supernovae, and quasars favor coasting cosmologies over the flat $Λ$CDM model |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2412.15717 |