New insights on a sign-switching Λ
Jorge F. Soriano, Shimon Wohlberg, Luis A. Anchordoqui
Abstract
The proposal for a sudden sign-switching cosmological constant Λ in the local universe, emulating a phase transition from anti-de Sitter (AdS) to de Sitter (dS) space, has markedly revamped the fit to observational data and lays out a propitious framework for ameliorating major cosmological tensions, such as the H 0 and S 8 tensions. This proposal is widely known as Λ s CDM. We investigate the possibility that Λ does not only flip sign at the transition but has also different curvature radii in the AdS and dS phases. We show that the critical redshift of the transition z c is strongly correlated with the vacuum energy in the AdS phase Ω Λ − , and that these two variables do not correlate strongly with the other cosmological parameters . We also show that the cost of adding an additional parameter to the Λ s CDM cosmological model does not improve the goodness of fit . Armed with our findings, we demonstrate that for a proper choice of z c , the vacuum energy in the dS phase may not necessarily be − Ω Λ − , for comparable degree of conformity between the model prediction and experimental data.