Non-comoving Cosmology

One of the fundamental assumptions of the standard \(\Lambda\)CDM 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....

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Bibliographic Details
Published in:arXiv.org 2019-03
Main Authors: Cembranos, J A R, Maroto, A L, Villarrubia-Rojo, H
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Cosmology
Density
Fluids
Isotropy
Large scale structure of the universe
Phenomenology
Relativistic velocity
Universe
Vorticity
Online Access:Get full text
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Summary:One of the fundamental assumptions of the standard \(\Lambda\)CDM 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 \(\Lambda\)CDM with the addition of a single free parameter \(\beta_0\), 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 \(\beta_0
ISSN:2331-8422
DOI:10.48550/arxiv.1903.11009