Cosmology in ghost-free bigravity theory with twin matter fluids: The origin of "dark matter"

Understand

We study dynamics of Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime based on the ghost-free bigravity theory.

• Assuming the coupling parameters guaranteeing the existence of de Sitter space as well as Minkowski spacetime, we find two stable attractors for spacetime with "twin" dust matter fields: One is de Sitter accelerating universe and the other is matter dominated universe.
• Although a considerable number of initial data leads to de Sitter universe, we also find matter dominated universe or spacetime with a future singularity for some initial data.
• The cosmic no-hair conjecture does not exactly hold, but the accelerating expansion can be found naturally.