Do cosmological observations allow a negative $\Lambda$?

Abstract

In view of the recent measurement of $H_0$ from HST and SH0ES team, we explore the possibility of existence of a negative cosmological constant (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 $\Lambda$CDM model using a different combination of CMB, SnIa, BAO and $H_0$ data. Various model comparison estimators show that quintessence models with a negative $\Lambda$ is either preferred over $\Lambda$CDM or performs equally as $\Lambda$CDM model. This suggests that the presence of a negative $\Lambda$ (AdS ground state) in our Universe, which can naturally arise in string theory, is consistent with cosmological observations.

Comments: 9 pages, Latex style, 6 figures, 6 tables, Revised version with new discussions and results, Accepted for publication in MNRAS