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Theoretical modeling reveals a smooth late-time AdS-to-dS transition in General Relativity, suggesting a viable mechanism to resolve cosmological tensions.
We present Ph-[Formula: see text]CDM, a phantom-scalar realization within General Relativity of the sign-switching cosmological-constant idea, [Formula: see text]CDM, in which a phantom scalar evolving on a bounded hyperbolic-tangent potential induces a smooth mirror AdS-to-dS transition in the late-time dark-energy density. The wrong-sign kinetic term, usually viewed as pathological, becomes the mechanism lifting the field from a negative- to a positive-energy vacuum-like regime. The construction also shows that the field can become repulsive while its energy density is still negative. The cosmology nevertheless remains controlled: total energy stays positive, the late-time attractor is de Sitter rather than a Big Rip, and the dynamics remain safely infrared. Ph-[Formula: see text]CDM thus offers a concrete late-time mechanism with the potential to address multiple cosmological tensions.
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Akarsu et al. (2026) studied this question.
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