Backreaction: directions of progress

@article{Rasanen2011BackreactionDO,
  title={Backreaction: directions of progress},
  author={Syksy Rasanen},
  journal={arXiv: Cosmology and Nongalactic Astrophysics},
  year={2011}
}
  • S. Rasanen
  • Published 2 February 2011
  • Physics
  • arXiv: Cosmology and Nongalactic Astrophysics
Homogeneous and isotropic cosmological models with ordinary matter and gravity predict slower expansion and shorter distances than observed. It is possible that this failure is due the known breakdown of homogeneity and isotropy related to structure formation, rather than new fundamental physics. We review this backreaction conjecture, concentrating on topics on which there has been progress as well as open issues. 

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References

SHOWING 1-10 OF 95 REFERENCES

Dark energy from backreaction

We consider the effect of inhomogeneities on the expansion of the Einstein–de Sitter universe. We find that the back-reaction of linear scalar metric perturbations results in apparent dark energy

On average properties of inhomogeneous cosmologies

The present talk summarizes the recently progressed state of a systematic re-evaluation of cosmological models that respect the presence of inhomogeneities. Emphasis is given to identifying the basic

Applicability of the linearly perturbed FRW metric and Newtonian cosmology

It has been argued that the effect of cosmological structure formation on the average expansion rate is negligible, because the linear approximation to the metric remains applicable in the regime of

Accelerated expansion from structure formation

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

Relativistic Cosmology: Its Nature, Aims and Problems

This paper discusses General Relativistic Aspects of Cosmology. Thus it will make only passing reference to astrophysical aspects of cosmology, and such features as GUTS, quantum gravity, etc. (these

Can Inhomogeneities Accelerate the Cosmic Volume Expansion

If expanding and contracting regions coexist in the universe, the speed of the cosmic volume expansion can be accelerated. We construct simple inhomogeneous dust-filled universe models in which the

The universe seen at different scales

COSMOLOGICAL ACCELERATION FROM STRUCTURE FORMATION

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.

Relativistic Cosmology. I

The paper presents some general relations obtaining in relativistic cosmology. It appears from these that a simple change over to anisotropy without the introduction of spin does not solve any of the

The possibility of cosmic acceleration via spatial averaging in Lemaître–Tolman–Bondi models

We investigate the possible occurrence of a positive cosmic acceleration in a spatially averaged, expanding, unbound Lemaître–Tolman–Bondi cosmology. By studying an approximation in which the
...