IA/U.Lisboa Seminar - A simple approach to the study of background cosmology in bigravity - 6 março 2017

In this talk I will consider two ansatzs relating the causal structure of two metrics that can allow us to investigate bigravity solutions in a simple way. For the solutions that satisfy the Generalized Gordon Ansatz the effect of the second gravitational sector is equivalent to that produced by a perfect fluid. On the other hand, this effect is equivalent to a null fluid for solutions fulfilling the Kerr-Schild Ansatz. I will apply this approach to cosmological solutions, noting that the Generalized Gordon solutions are described by FLRW metrics whereas the Kerr-Schild solutions imply a Bianchi I metric. In both cases the experimental measures of the CMB dipole impose restrictions on the magnitude of the velocities of the common cosmic fluids.