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Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant

Accepted version
Peer-reviewed

Type

Article

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Authors

Akarsu, Ö 
Barrow, JD 
Escamilla, LA 
Vazquez, JA 

Abstract

We study the cosmological constant in the standard CDM model by introducing the graduated dark energy (gDE) characterised by a minimal dynamical deviation from the null inertial mass density of the in the form inert / < 0 with < 1 being a ratio of two odd integers, for which its energy density dynamically takes negative values in the nite past. For large negative values of , it creates a phenomenological model described by a smooth function that approximately describes the spontaneously switching sign in the late universe to become positive today. We confront the model with the latest combined observational data sets of PLK+BAO+SN+H. It is striking that the data predict bimodal posterior probability distributions for the parameters of the model along with large negative values; the new maximum signi cantly excludes the , and the old maximum contains the . The improvement in the goodness of the t for the reaches highly signi cant levels, 2 min = 6:4, for the new maxima, while it remains at insigni cant levels, 2 min . 0:02, for the old maxima. We show that, in contrast to the old maxima, which do not distinguish from the , the new maxima agree with the model-independent H0 measurements, high-precision Ly- 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 AdS vacua to dS vacua, at a redshift z 2:32 and triggered the late-time acceleration, and suggests looking for such mechanisms in string theory constructions.

Description

Keywords

5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences

Journal Title

Physical Review D

Conference Name

Journal ISSN

2470-0010
2470-0029

Volume Title

101

Publisher

American Physical Society (APS)

Rights

All rights reserved
Sponsorship
Science and Technology Facilities Council (ST/P000673/1)