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arXiv · 2506.12139

Cosmographic analysis of sign-switching dark energy

Mariam Bouhmadi-López·Beñat Ibarra-Uriondo
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Abstract

Inspired by the well-studied $\Lambda_{\rm s}$CDM model, we propose and investigate a class of dynamical dark energy models that evolve from a negative cosmological constant, transitioning to a positive value at low redshifts. Specifically, we introduce a dark energy framework based on a generalised ladder-step function for the cosmological constant. Furthermore, we present two additional models in which the cosmological constant undergoes a smooth sign change at a specified redshift. We provide a detailed discussion of the construction and theoretical properties of these models, analysing their background cosmological evolution using a cosmographic approach and the statefinder hierarchy parameters. Our results are compared with those obtained for the standard $\Lambda$CDM and $\Lambda_{\rm s}$CDM models. We also perform a careful analysis of the types of singularities that may arise in these models due to a sign change in the cosmological constant. Notably, we show that a continuous sign change removes the sudden singularity present in the $\Lambda_{\rm s}$CDM model, replacing it with a milder $w$-singularity.

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Mariam Bouhmadi-López, Beñat Ibarra-Uriondo. 2025-06-13. Cosmographic analysis of sign-switching dark energy. https://doi.org/10.1103/v1cl-pr54

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