Abstract
We construct a three-dimensional, fully relativistic numerical model of a universe filled with an inhomogeneous pressureless fluid, starting from initial data that represent a perturbation of the Einstein–de Sitter model. We then measure the departure of the average expansion rate with respect to this homogeneous and isotropic reference model, comparing local quantities to the predictions of linear perturbation theory. We find that collapsing perturbations reach the turnaround point much earlier than expected from the reference spherical top-hat collapse model and that the local deviation of the expansion rate from the homogeneous one can be as high as 28% at an underdensity, for an initial density contrast of . We then study, for the first time, the exact behavior of the backreaction term . We find that, for small values of the initial perturbations, this term exhibits a scaling, and that it is negative with a linearly growing absolute value for larger perturbation amplitudes, thereby contributing to an overall deceleration of the expansion. Its magnitude, on the other hand, remains very small even for relatively large perturbations.
- Received 7 December 2015
DOI:https://doi.org/10.1103/PhysRevLett.116.251302
© 2016 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
A Relativistic View of a Clumpy Universe
Published 24 June 2016
Cosmologists have begun using fully relativistic models to understand the effects of inhomogeneous matter distribution on the evolution of the Universe.
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