Cosmological Models with Negative \(\varLambda \)

In recent years, concordance \(\varLambda \) CDM model is in trouble due to various cosmological tensions and anomalies. This has motivated cosmologists to explore beyond \(\varLambda \) CDM model to resolve these tensions and anomalies. In this regard, dark energy models with slightly negative behaviour at higher redshifts can be a potential candidate to resolve these tensions. Such behaviour can be easily incorporated with the presence of small negative cosmological constant. In recent years, there have been many efforts in this direction. In this article, we first motivate dark energy models in the presence of negative cosmological constant in the context of earlier observational results and then present a brief review of the recent research activities in this direction, especially in the context of cosmological tensions.