Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant
Dec 18, 2019
14 pages
Published in:
- Phys.Rev.D 101 (2020) 6, 063528
- Published: Mar 25, 2020
e-Print:
- 1912.08751 [astro-ph.CO]
DOI:
- 10.1103/PhysRevD.101.063528 (publication)
View in:
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Abstract: (APS)
We study the cosmological constant (Λ) in the standard Λ cold dark matter model by introducing the graduated dark energy (gDE) characterized by a minimal dynamical deviation from the null inertial mass density of the Λ in the form ρinert∝ρλ<0 with λ<1 being a ratio of two odd integers, for which its energy density ρ dynamically takes negative values in the finite past. For large negative values of λ, it creates a phenomenological model described by a smooth function that approximately describes the Λ spontaneously switching sign in the late Universe to become positive today. We confront the model with the latest combined observational datasets of Planck+baryon acoustic oscillations+supernova+H. It is striking that the data predict bimodal posterior probability distributions for the parameters of the model along with large negative λ values; the new maximum significantly excludes the Λ, and the old maximum contains the Λ. The improvement in the goodness of fit for the Λ reaches highly significant levels, Δχmin2=6.4, for the new maxima, while it remains at insignificant levels, Δχmin2≲0.02, for the old maxima. We show that, in contrast to the old maxima, which do not distinguish from the Λ, the new maxima agree with the model-independent H0 measurements, high-precision Ly-α data, and model-independent Omh2 diagnostic estimates. Our results provide strong hints of a spontaneous sign switch in the cosmological constant and lead us to conjecture that the Universe has transitioned from anti-de Sitter vacua to de Sitter vacua, at a redshift z≈2.32, and triggered the late-time acceleration, and suggests looking for such mechanisms in string theory constructions.Note:
- 14 pages, 7 figures, 2 tables; matches the version to appear in PRD
- Cosmology
- vacuum state: anti-de Sitter
- energy: density
- mass: density
- cosmological constant
- dark energy
- cosmological model
- expansion: acceleration
- string model
- Hubble constant
References(115)
Figures(11)
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