# Evaluating backreaction with the ellipsoidal collapse model

@article{Montanari2017EvaluatingBW, title={Evaluating backreaction with the ellipsoidal collapse model}, author={Francesco Montanari and Syksy R{\"a}s{\"a}nen}, journal={Journal of Cosmology and Astroparticle Physics}, year={2017}, volume={2017}, pages={008 - 008} }

We evaluate the effect of structure formation on the average expansion rate with a statistical treatment where density peaks and troughs are modelled as homogeneous ellipsoids. This extends earlier work that used spherical regions. We find that the shear and the presence of filamentary and planar structures have only a small impact on the results. The expansion rate times the age of the universe Ht increases from 2/3 to 0.83 at late times, in order of magnitude agreement with observations…

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## References

SHOWING 1-10 OF 214 REFERENCES

Evaluating backreaction with the peak model of structure formation

- Physics
- 2008

We evaluate the average expansion rate of a universe which contains a realistic evolving ensemble of non-linear structures. We use the peak model of structure formation to obtain the number density…

Ellipsoidal Collapse and Previrialization

- Physics
- 2001

We study the nonlinear evolution of a dust ellipsoid embedded in a flat Friedmann background universe, in order to determine the evolution of the density of the ellipsoid as the perturbation…

The growth of aspherical structure in the universe - Is the Local Supercluster an unusual system

- Physics
- 1979

The growth and subsequent collapse of homogeneous ellipsoidal perturbations in a uniform expanding background is considered as a simple model for the formation of large-scale aspherical structures in…

Effects of Nonlinear Inhomogeneity on the Cosmic Expansion with Numerical Relativity.

- PhysicsPhysical review letters
- 2016

It is found 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 10^{-2}.

Accelerated expansion from structure formation

- Physics, Geology
- 2006

We discuss the physics of backreaction-driven accelerated expansion. Using the exact equations for the behaviour of averages in dust universes, we explain how large-scale smoothness does not imply…

COSMOLOGICAL ACCELERATION FROM STRUCTURE FORMATION

- Physics
- 2006

We discuss the Buchert equations, which describe the average expansion of an inhomogeneous dust universe. In the limit of small perturbations, they reduce to the Friedmann–Robertson–Walker equations.…

On the evolution of aspherical perturbations in the universe: an analytical model

- Physics
- 2002

I study the role of shear fields on the evolution of density perturbations by using an analytical approximate solution for the equations of motion of homogeneous ellipsoids embedded in a homogeneous…

An Analytical Model for the Triaxial Collapse of Cosmological Perturbations

- Physics
- 1994

We present an analytical model for the non-spherical collapse of overdense regions out of a Gaussian random field of initial cosmological perturbations. The collapsing region is treated as an…

Ellipsoidal collapse and an improved model for the number and spatial distribution of dark matter haloes

- Physics
- 2001

The Press–Schechter, excursion set approach allows one to make predictions about the shape and evolution of the mass function of bound objects. The approach combines the assumption that objects…

Back reaction of inhomogeneities on the expansion: The evolution of cosmological parameters

- Physics
- 2000

Averaging and evolving inhomogeneities are non-commuting operations. This implies the existence of deviations of an averaged model from the standard Friedmann-Lemaitre cosmologies. We quantify these…