Cosmological histories in bimetric gravity: A graphical approach

Understand

The bimetric generalization of general relativity has been proven to be able to give an accelerated background expansion consistent with observations.

• Apart from the energy densities coupling to one or both of the metrics, the expansion will depend on the cosmological constant contribution to each of them, as well as the three parameters describing the interaction between the two metrics.
• Even for fixed values of these parameters can several possible solutions, so called branches, exist.
• Different branches can give similar background expansion histories for the observable metric, but may have different properties regarding, for example, the existence of ghosts and the rate of structure growth.