Ponente
Descripción
One of the fundamental assumptions of the standard LCDM cosmology is that, on large scales, all the matter-energy components of the Universe share a common rest frame. This seems natural for the visible sector, that has been in thermal contact and tightly coupled in the primeval Universe. The dark sector, on the other hand, does not have any non-gravitational interaction known to date and therefore, there is no a priori reason to impose that it is comoving with ordinary matter. In this work we explore the consequences of relaxing this assumption and study the cosmology of non-comoving fluids. We show that it is possible to construct a homogeneous and isotropic cosmology with a collection of fluids moving with non-relativistic velocities. Our model extends LCDM with the addition of a single free parameter eta_0, the initial velocity of the visible sector with respect to the frame that observes a homogeneous and isotropic universe. This modification gives rise to a rich phenomenology, while being consistent with current observations for eta_0<1.6e-3 n (95% CL). Among the observable effects we find: sizeable modifications in the density-velocity and density-lensing potential cross-correlation spectra for matter, violations of CMB statistical isotropy and production of vorticity and cosmological magnetic fields through new couplings between scalar and vector modes.
