Cosmology and Stability in Scalar-Tensor bigravity

The bigravity models coupled with two scalar fields are constructed. We show that a wide class of the expansion history of the universe, especially corresponding to dark energy and/or inflation, can be described by a solution of the bigravity model. We discuss the stability of the solution and give the conditions for the stability. We also explicitly construct a model which gives a stable solution. By using the stable model, for an arbitrary evolution of the universe expansion, we construct the Brans-Dicke like model which reproduces the evolution.

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Date added: Tue, 8 Oct 13