Do cosmological observations allow a negative $\Lambda$?
  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 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 combination of CMB+lensing+SnIa+BAO+$H_{0}$ data. Various model
comparison estimators show that quintessence models with a negative $\Lambda$
is always preferred over $\Lambda$CDM. This confirms 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.
