Kei-ichi Maeda, Mikhail S. Volkov
We study Bianchi cosmologies in the ghost-free bigravity theory assuming both metrics to be homogeneous and anisotropic, of Bianchi class A, which includes types I,II,VI$_0$,VII$_0$,VIII, and IX. We assume the universe to contain a radiation and a non-relativistic matter, with the cosmological term mimicked by the graviton mass. We find that, for generic initial values leading to a late-time self-acceleration, the universe approaches a state with non-vanishing anisotropies, whose contribution to the total energy density decreases following the low of a non-relativistic matter. This is a much slower falloff than in General Relativity, therefore this could lead to observational effects. The solutions show a singularity in the past, and in the Bianchi IX case the singularity is approached via a sequence of Kasner-like steps, which is characteristic for a chaotic behavior.
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http://arxiv.org/abs/1302.6198
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