Cosmology Beyond Einstein pp 55-70 | Cite as

# Cosmological Stability of Massive Bigravity

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## Abstract

In the previous chapter, and in particular in Sect. 2.1, we discussed an approach to modifying gravity in which its force-carrier particle, the graviton, is given a small mass. In particular, by specialising to the dRGT interaction potentials ( 2.22) we ensure that the notorious Boulware-Deser ghost mode is absent, and by allowing both metrics to be dynamical and taking the graviton mass to be of the order of the present-day Hubble rate, we can obtain cosmological solutions which agree well with observations of the cosmic expansion history. These solutions are self-accelerating: the Hubble parameter goes to a constant at late times even in the absence of a cosmological constant. The action of this bimetric theory, or *bigravity*, is given by Eq. ( 2.30), and the associated modified gravitational field equations were presented as Eqs. ( 2.39) and ( 2.40).

## Keywords

Cosmological Constant Auxiliary Variable Bimetric Theory Perturbation Variable Hubble Rate## References

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