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New insights on a sign-switching $\Lambda$

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arxiv 2502.19239 v1 pith:WTN3Z6H6 submitted 2025-02-26 astro-ph.CO

classification astro-ph.CO
keywords lambdacosmologicalphasetransitiondataenergymodelomega
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

The proposal for a sudden sign-switching cosmological constant $\Lambda$ 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 $\Lambda_s$CDM. We investigate the possibility that $\Lambda$ 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 $\Omega_{\Lambda_-}$, 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 $\Lambda_s$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 $-\Omega_{\Lambda_-}$, for comparable degree of conformity between the model prediction and experimental data.

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Cited by 7 Pith papers

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