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 AsCDM model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)]. 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 & DAG; ' 2, inspired by the graduated dark energy model proposed in Akarsu et al. [Phys. Rev. D 101, 063528 (2020)]. AsCDM was previously claimed to simultaneously relax five cosmological discrepancies, namely, the H0, S8, and MB tensions along with the Ly-& alpha; and cob anomalies, which prevail within the standard ACDM 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 AsCDM exhibits a better fit to the data compared to ACDM, and simultaneously relaxes the six discrepancies of ACDM, viz., the H0, MB, S8, Ly-& alpha;, t0, and cob discrepancies, all of which are discussed in detail. When the MB prior is included in the analyses, AsCDM performs significantly better in relaxing the H0, MB, and S8 tensions with the constraint z & DAG; ' 1.8 even when the Ly-& alpha; data (which imposed the z & DAG; ' 2 constraint in the previous studies) are excluded. In contrast, the presence of the MB prior causes only negligible improvements for ACDM. Thus, the AsCDM model provides remedy to various cosmological tensions simultaneously, only that the galaxy BAO data hinder its success to some extent.