Constraining deviations from $Λ$CDM in the Hubble expansion rate
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arXiv
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866917107089801216 |
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| author | Yang, Yupeng |
| author_facet | Yang, Yupeng |
| contents | The $Λ$CDM cosmolgical model has long been regarded as highly successful in accurately describing a wide range of astronomical observations. However, numerous observational findings have also provided hints of discrepancies from the predictions of the $Λ$CDM framework. We explore a phenomenological model that quantifies the deviation of the Hubble expansion rate from the standard scenario, which is expressed as $H^{2}(z) = H^{2}_{\rm ΛCDM}(Ω_m, z)[1+δ(z)]$. We consider three distinct forms for the deviation parameter $δ(z)$: in model I, $δ(z)=δ_c$; in model II, $δ(z)=δ_{c}z/(1+z)$, and in model III, $δ(z)=δ_{c}{\rm ln}(1+z)$. Here, $δ_c$ represents a constant value. We utilize a comprehensive set of observational data to constrain the models. Our results show that for most combined datasets, $δ_c$ tends to take on negative values for models I and II, while consistently taking positive values in model III. Furthermore, we find that both models I and II remain consistent with the standard $Λ$CDM model across all datasets examined. In contrast, model III exhibits a significant deviation from the $Λ$CDM model, exceeding $2σ$ for the full combined datastes. The AIC indicates that models I and II are consistent with the $Λ$CDM model, whereas model III is preferred over the standard $Λ$CDM model, with the $Λ$CDM model being disfavored for the combined datasets DESI BAO + CMB + CC + DESY5. These results suggest that the Hubble expansion rate likely deviates from the standard $Λ$CDM prediction. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_17848 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Constraining deviations from $Λ$CDM in the Hubble expansion rate Yang, Yupeng Cosmology and Nongalactic Astrophysics The $Λ$CDM cosmolgical model has long been regarded as highly successful in accurately describing a wide range of astronomical observations. However, numerous observational findings have also provided hints of discrepancies from the predictions of the $Λ$CDM framework. We explore a phenomenological model that quantifies the deviation of the Hubble expansion rate from the standard scenario, which is expressed as $H^{2}(z) = H^{2}_{\rm ΛCDM}(Ω_m, z)[1+δ(z)]$. We consider three distinct forms for the deviation parameter $δ(z)$: in model I, $δ(z)=δ_c$; in model II, $δ(z)=δ_{c}z/(1+z)$, and in model III, $δ(z)=δ_{c}{\rm ln}(1+z)$. Here, $δ_c$ represents a constant value. We utilize a comprehensive set of observational data to constrain the models. Our results show that for most combined datasets, $δ_c$ tends to take on negative values for models I and II, while consistently taking positive values in model III. Furthermore, we find that both models I and II remain consistent with the standard $Λ$CDM model across all datasets examined. In contrast, model III exhibits a significant deviation from the $Λ$CDM model, exceeding $2σ$ for the full combined datastes. The AIC indicates that models I and II are consistent with the $Λ$CDM model, whereas model III is preferred over the standard $Λ$CDM model, with the $Λ$CDM model being disfavored for the combined datasets DESI BAO + CMB + CC + DESY5. These results suggest that the Hubble expansion rate likely deviates from the standard $Λ$CDM prediction. |
| title | Constraining deviations from $Λ$CDM in the Hubble expansion rate |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2508.17848 |