2025/03/17 by Luis A. Escamilla, Özgür Akarsu, Escamilla, Luis A. +7
Physics and Astronomy · #Astronomy and Astrophysical Research #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.2503.12945
openalex publication_date 2025/03/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 ΛCDM framework, a combination of Planck and fσ8 data yields γ≈ 0.64, in ∼4σ tension with the theoretically expected value γ≈ 0.55 (assuming general relativity). This discrepancy, closely related to the S8 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 sCDM framework (featuring a rapid sign-switching cosmological constant (mirror AdS-to-dS transition) in the late universe at redshift z_† ∼ 2 ) can simultaneously alleviate the γ, H0 , and S8 tensions. We also examined a scenario with fixed z_† = 1.7 , previously identified as a sweet spot for alleviating multiple major cosmological tensions (including those in H0 , MB , and S8 ) finding that it completely eliminates both the γ and H0 tensions, although it is statistically disfavored by our dataset combinations. Our findings suggest that Λ\rm sCDM is a promising model, providing a potential unified resolution to multiple major cosmological tensions.