Kinematical and dynamical aspects of ghost-matter cosmologies

Understand

We consider the kinematical and dynamical evolution of Friedmann universes with a mixture of non-interacting matter and a ghost-like field, in a scenario analogous to that advocated by the Quintom model.

• Assuming that the conventional matter dominates today, we find that the ghost component can bring the future expansion and the past contraction of the model to a finite halt.
• Moreover, at the moment the expansion or contraction stops, we find that the tendency of the universe is to bounce back and re-collapse or re-expand.
• Therefore, the presence of a (never dominant) ghost-field with negative density could, in principle, drive the universe into an eternal cycle of finite expansion, collapse, and re-expansion.