# Backreaction in Late-Time Cosmology

@article{Buchert2011BackreactionIL, title={Backreaction in Late-Time Cosmology}, author={Thomas Buchert and Syksy Rasanen}, journal={Annual Review of Nuclear and Particle Science}, year={2011}, volume={62}, pages={57-79} }

We review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature, and light propagation in the universe, focusing on the possibility that this effect could explain cosmological observations without requiring the introduction of dark energy or modified gravity. We concentrate on explaining the relevant physics and highlighting open questions.

## 196 Citations

### Backreaction in the future behavior of an expanding vacuum spacetime

- Physics
- 2018

We perform a rescaling analysis to analyze the future behavior of a class of T2-symmetric vacuum spacetimes. We show that on the universal cover, there is C0-convergence to a spatially homogeneous…

### A toy cosmological model with dynamical backreaction

- Physics
- 2015

In this paper, the Buchert averaging of the Dust Shell Universe is explicitly carried out. The dynamical backreaction does not vanish in such a model. Instead, it acts as the possible source of the…

### Backreaction of Quantum Gravitational Modes

- PhysicsGravitational Theories Beyond General Relativity
- 2019

Effective Field Theory methods are employed to investigate the leading order quantum corrections to the backreaction of gravitational waves. The effective energy-momentum tensor is computed and we…

### A stronger case for self-interacting dark matter

- Physics
- 2019

We explore a gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling it condensates to super-structures…

### The Newtonian Limit on Cosmological Scales

- Physics, Mathematics
- 2014

We establish the existence of a wide class of inhomogeneous relativistic solutions to the Einstein–Euler equations that are well approximated on cosmological scales by solutions of Newtonian gravity.…

### Cosmic acceleration driven by dark matter self-interactions

- Physics
- 2019

We explore a Gedanken-model for cosmic evolution, where dark matter is strongly self-interacting and stays in a plasma state until late stages. After decoupling, it condensates to super-structures…

### Numerical relativity investigation of the effects of gravitational waves on the inhomogeneity of the universe

- PhysicsThe European Physical Journal C
- 2018

We numerically integrate the Einstein’s equations for a spatially flat Friedmann–Lemaire–Robertson–Walker (FLRW) background spacetime with a spatial curvature perturbation and evolving primordial…

### Cosmological back-reaction in modified gravity and its implications for dark energy

- Physics
- 2014

We study the effective stress-energy tensor induced by cosmological inhomogeneity in f(R)=R+c R2 and equivalent scalar-tensor theories, motivated both by models of early universe inflation and by…

### Backreaction mechanism in multifluid and extended cosmologies

- Physics
- 2014

One possible explanation for the present observed acceleration of the Universe is the breakdown of homogeneity and isotropy due to the formation of non-linear structures. How inhomogeneities affect…

### A gradient expansion for cosmological backreaction

- Physics
- 2012

We address the issue of cosmological backreaction from non-linear structure formation by constructing an approximation for the time evolved metric of a dust dominated universe based on a gradient…

## References

SHOWING 1-10 OF 203 REFERENCES

### Dark energy from backreaction

- Physics
- 2003

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…

### Backreaction of linear perturbations and dark energy

- Physics
- 2004

A simple discussion on the backreaction of inhomogeneities in cosmology, focusing on the possibility that it could explain the present acceleration and solve the coincidence problem.

### Backreaction: directions of progress

- Physics
- 2011

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…

### BACKREACTION PROBLEM FOR COSMOLOGICAL PERTURBATIONS

- Physics
- 1997

We derive the effective energy-momentum tensor for cosmological perturbations and prove its gauge-invariance. The result is applied to study the influence of perturbations on the behaviour of the…

### Applicability of the linearly perturbed FRW metric and Newtonian cosmology

- Physics
- 2010

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…

### On the Back Reaction Problem for Gravitational Perturbations

- Physics
- 1996

We derive the eﬀective energy-momentum tensor for cosmological perturbations and prove its gauge-invariance. The result is applied to study the inﬂuence of perturbations on the behaviour of the…

### 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…

### Constraints on backreaction in dust universes

- Physics
- 2006

We study backreaction in dust universes using exact equations which do not rely on perturbation theory, concentrating on theoretical and observational constraints. In particular, we discuss the…