$Λ_{\rm s}$CDM model: A promising scenario for alleviation of cosmological tensions

Abstract

We present a comprehensive analysis of the $Λ_{\rm s}$CDM model, which explores the recent conjecture suggesting a rapid transition of the Universe from anti-de Sitter vacua to de Sitter vacua (viz., the cosmological constant switches sign from negative to positive) at redshift ${z_\dagger\sim 2}$, inspired by the graduated dark energy (gDE) model. Our analysis shows that, predicting $z_\dagger\approx1.7$, $Λ_{\rm s}$CDM simultaneously addresses the major cosmological tensions of the standard $Λ$CDM model, viz., the Hubble constant $H_0$, the Type Ia Supernovae absolute magnitude $M_{\rm B}$, and the growth parameter $S_8$ tensions, along with other less significant tensions such as the BAO Lyman-$α$ discrepancy.

Figures (3)

• Figure 1: 2D contours at 68% and 95% CLs in the $H_0$-$\Omega_{\rm m}$ plane for the $\Lambda_{\rm s}$CDM and $\Lambda$CDM models from the Planck and/or BAOtr data. It deserves mention that, in case of $\Lambda_{\rm s}$CDM, the Planck and BAOtr contours intersect right on the vertical band of SH0ES measurement.
• Figure 2: 2D contours at 68% and 95% CLs in the $\Omega_{\rm m}$-$S_8$ plane for the $\Lambda_{\rm s}$CDM and $\Lambda$CDM models. $S_8 = 0.801^{+0.026}_{-0.016}$ ($\Lambda_{\rm s}$CDM: Planck), $S_8 = 0.746^{+0.026}_{-0.021}$ ($\Lambda_{\rm s}$CDM: KiDS-1000), $S_8 = 0.832\pm 0.013$ ($\Lambda$CDM: Planck), $S_8 =0.749^{+0.027}_{-0.020}$ ($\Lambda$CDM: KiDS-1000) at 68% CL.
• Figure 3: The mean values with 68% CL on $H_0$ for the $\Lambda_{\rm s}$CDM and $\Lambda$CDM models from various data combinations. The left vertical band stands for Planck-$\Lambda$CDM constraint: $H_0=67.36\pm0.54{\rm \,km\, s^{-1}\, Mpc^{-1}}$, and the right one is for the latest SH0ES measurement Riess:2021jrx: $H_0=73.04\pm1.04{\rm \,km\, s^{-1}\, Mpc^{-1}}$. We see that there is no $H_0$ tension in most data combinations for $\Lambda_{\rm s}$CDM, in particular, when we use the less model-dependent BAOtr data. The only exception is in the cases explored in previous works Akarsu:2021folAkarsu:2022typ that employ the 3D BAO data (BAO in the plot), among which the two galaxy BAO data from $z_{\rm eff}=0.15$ and $0.38$ preventing the model from successfully resolving the tension.