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arXiv · 2508.09813

Dynamical dark energy in models with evolution close to $\Lambda$CDM

Saikat Chakraborty·Charlotte Louw·Peter K. S. Dunsby·Kelly MacDevette·Alvaro de la Cruz Dombriz
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Abstract

In this communication we address whether or not there is an equivalence between the kinematical and dynamical descriptions of the spatially flat $\Lambda$CDM model. We address this by investigating whether an almost $\Lambda$CDM expansion history ($j(z)\approx1$) corresponds to an almost $\Lambda$CDM model ($w_{\rm DE}(z)\approx-1$) by considering two particular explicit examples. At least for the cases considered, this turns out not to be the case. Instead, what we find is that an almost $\Lambda$CDM cosmic evolution rather corresponds to an \emph{almost unified dark fluid model}. Considering that one never gets the exact condition $j(z)=1$ from any cosmographic data sets, this raises further questions on whether the $\Lambda$CDM model is the best candidate for the standard model of the evolution of the universe.

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Saikat Chakraborty, Charlotte Louw, Peter K. S. Dunsby, Kelly MacDevette, Alvaro de la Cruz Dombriz. 2025-08-13. Dynamical dark energy in models with evolution close to $\Lambda$CDM. https://arxiv.org/abs/2508.09813

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