Negative cosmological constant in the dark sector?

Understand

We consider the possibility that the dark sector of our Universe contains a negative cosmological constant dubbed $\lambda$.

• For such models to be viable, the dark sector should contain an additional component responsible for the late-time accelerated expansion rate ($X$).
• We explore the departure of the expansion history of these models from the concordance $\Lambda$ Cold Dark Matter model.
• For a large class of our models the accelerated expansion is transient with a nontrivial dependence on the model parameters.