We study Bianchi cosmologies in the ghost-free bigravity theory, assuming both metrics to be homogeneous and anisotropic and of the Bianchi class A, which includes types I, II, VI0, VII0, VIII, and IX. We assume the Universe to contain a radiation and a nonrelativistic 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 nonvanishing anisotropies. The anisotropy contribution to the total energy density decreases much slower than in General Relativity and shows the same falloff rate as the energy of a nonrelativistic matter. 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 of a chaotic behavior.
|ジャーナル||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|出版ステータス||Published - 2013 5 7|
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