Do cosmological observations allow a negative Λ?

Abstract

In view of the recent measurement of H0 from the Hubble Space Telescope and Supernova H0 for the Equation of State (SH0ES) team, we explore the possibility of existence of a negative cosmological constant [anti-de Sitter (AdS) vacua in the dark energy sector] in the Universe. In this regard, we consider quintessence fields on top of a negative cosmological constant and compare such construction with Λ cold dark matter (ΛCDM) model using a different combination of cosmic microwave background, Type Ia supernova, baryon acoustic oscillation, and H0 data. Various model comparison estimators show that quintessence models with a negative Λ are either preferred over ΛCDM or perform equally as the ΛCDM model. This suggests that the presence of a negative Λ (AdS ground state) in our Universe, which can naturally arise in string theory, is consistent with cosmological observations.