Exploring the Growth-Index ($γ$) Tension with $Λ_{\rm s}$CDM
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arXiv
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| Auteurs principaux: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866916656520888320 |
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| author | Escamilla, Luis A. Akarsu, Özgür Di Valentino, Eleonora Özülker, Emre Vazquez, J. Alberto |
| author_facet | Escamilla, Luis A. Akarsu, Özgür Di Valentino, Eleonora Özülker, Emre Vazquez, J. Alberto |
| contents | Recent observational analyses have revealed a significant tension in the growth index $γ$, which characterizes the growth rate of cosmic structures. Specifically, when treating $γ$ as a free parameter within $Λ$CDM framework, a combination of Planck and $ fσ_8 $ data yields $γ\approx 0.64$, in $\sim4σ$ tension with the theoretically expected value $γ\approx 0.55$ (assuming general relativity). This discrepancy, closely related to the $ S_8 $ tension, poses a new challenge to the standard cosmological model by suggesting that it predicts an excessive growth of structure. In this work, we demonstrate that the $Λ_{\rm s}$CDM framework (featuring a rapid sign-switching cosmological constant (mirror AdS-to-dS transition) in the late universe at redshift $ z_\dagger \sim 2 $) can simultaneously alleviate the $ γ$, $ H_0 $, and $ S_8 $ tensions. We also examined a scenario with fixed $ z_\dagger = 1.7 $, previously identified as a sweet spot for alleviating multiple major cosmological tensions (including those in $ H_0 $, $ M_B $, and $ S_8 $) finding that it completely eliminates both the $ γ$ and $ H_0 $ tensions, although it is statistically disfavored by our dataset combinations. Our findings suggest that $Λ_{\rm s}$CDM is a promising model, providing a potential unified resolution to multiple major cosmological tensions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_12945 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Exploring the Growth-Index ($γ$) Tension with $Λ_{\rm s}$CDM Escamilla, Luis A. Akarsu, Özgür Di Valentino, Eleonora Özülker, Emre Vazquez, J. Alberto Cosmology and Nongalactic Astrophysics Recent observational analyses have revealed a significant tension in the growth index $γ$, which characterizes the growth rate of cosmic structures. Specifically, when treating $γ$ as a free parameter within $Λ$CDM framework, a combination of Planck and $ fσ_8 $ data yields $γ\approx 0.64$, in $\sim4σ$ tension with the theoretically expected value $γ\approx 0.55$ (assuming general relativity). This discrepancy, closely related to the $ S_8 $ tension, poses a new challenge to the standard cosmological model by suggesting that it predicts an excessive growth of structure. In this work, we demonstrate that the $Λ_{\rm s}$CDM framework (featuring a rapid sign-switching cosmological constant (mirror AdS-to-dS transition) in the late universe at redshift $ z_\dagger \sim 2 $) can simultaneously alleviate the $ γ$, $ H_0 $, and $ S_8 $ tensions. We also examined a scenario with fixed $ z_\dagger = 1.7 $, previously identified as a sweet spot for alleviating multiple major cosmological tensions (including those in $ H_0 $, $ M_B $, and $ S_8 $) finding that it completely eliminates both the $ γ$ and $ H_0 $ tensions, although it is statistically disfavored by our dataset combinations. Our findings suggest that $Λ_{\rm s}$CDM is a promising model, providing a potential unified resolution to multiple major cosmological tensions. |
| title | Exploring the Growth-Index ($γ$) Tension with $Λ_{\rm s}$CDM |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2503.12945 |