Assessing observational constraints on dark energy

David Shlivko; Paul Steinhardt

doi:10.1016/j.physletb.2024.138826

paper

Assessing observational constraints on dark energy

arXiv:2405.03933 · doi:10.1016/j.physletb.2024.138826

Abstract

Observational constraints on time-varying dark energy ({\it e.g.}, quintessence) are commonly presented on a $w_{0}$ - $w_{a}$ plot that assumes the equation of state of dark energy strictly satisfies $w (z) = w_{0} + w_{a} z / (1 + z)$ as a function of the redshift $z$ . Recent observations favor a sector of the $w_{0}$ - $w_{a}$ plane in which $w_{0} > - 1$ and $w_{0} + w_{a} < - 1$ , suggesting that the equation of state underwent a transition from violating the null energy condition (NEC) at large $z$ to obeying it at small $z$ . In this paper, we demonstrate that this impression is misleading by showing that simple quintessence models satisfying the NEC for all $z$ predict an observational preference for the same sector. We also find that quintessence models that best fit observational data can predict a value for the dark energy equation of state at present that is significantly different from the best-fit value of $w_{0}$ obtained assuming the parameterization above. In addition, the analysis reveals an approximate degeneracy of the $w_{0}$ - $w_{a}$ parameterization that explains the eccentricity and orientation of the likelihood contours presented in recent observational studies.

14 pages, 4 figures. Typo fixed in v2

Assessing observational constraints on dark energy

Abstract

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