Relaxing cosmological tensions with a sign switching cosmological constant: Improved results with Planck, BAO, and Pantheon data

We present a further observational analysis of the ΛsCDM model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)PRVDAQ2470-001010.1103/PhysRevD.104.123512]. This model is based on the recent conjecture suggesting the Universe has transitioned from anti-de Sitter vacua to de Sitter vacua (viz., the cosmological constant switches sign from negative to positive), at redshift z†∼2, inspired by the graduated dark energy model proposed in Akarsu et al. [Phys. Rev. D 101, 063528 (2020)PRVDAQ2470-001010.1103/PhysRevD.101.063528]. ΛsCDM was previously claimed to simultaneously relax five cosmological discrepancies, namely, the H0, S8, and MB tensions along with the Ly-α and ωb anomalies, which prevail within the standard ΛCDM model as well as its canonical/simple extensions. In the present work, we extend the previous analysis by constraining the model using the Pantheon data (with and without the SH0ES MB prior) and/or the completed BAO data along with the full Planck CMB data. We find that ΛsCDM exhibits a better fit to the data compared to ΛCDM, and simultaneously relaxes the six discrepancies of ΛCDM, viz., the H0, MB, S8, Ly-α, t0, and ωb discrepancies, all of which are discussed in detail. When the MB prior is included in the analyses, ΛsCDM performs significantly better in relaxing the H0, MB, and S8 tensions with the constraint z†∼1.8 even when the Ly-α data (which imposed the z†∼2 constraint in the previous studies) are excluded. In contrast, the presence of the MB prior causes only negligible improvements for ΛCDM. Thus, the ΛsCDM model provides remedy to various cosmological tensions simultaneously, only that the galaxy BAO data hinder its success to some extent.