author={Alessio Notari},
  journal={Modern Physics Letters A},
  • A. Notari
  • Published 31 March 2005
  • Physics
  • Modern Physics Letters A
It is widely believed that the assumption of homogeneity is a good zeroth order approximation for the expansion of our Universe. We analyze the correction due to subhorizon inhomogeneous gravitational fields. While at early times this contribution (which may act as a negative pressure component) is perturbatively subdominant, we show that the perturbative series is likely to diverge at redshift of order 1, due to the growth of perturbations. So, the homogeneous Friedmann equation cannot be… 
Onset of cosmological backreaction
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The Averaging Problem in Cosmology
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Influence of structure formation on the cosmic expansion
We investigate the effect that the average backreaction of structure formation has on the dynamics of the cosmological expansion, within the concordance model. Our approach in the Poisson gauge is
Backreaction of inhomogeneities can mimic dark energy
In the standard approach to cosmology, the evolution and observations associated with an inhomogeneous universe with density p(x) are modeled by employing a homogeneous cosmological model of density
Inhomogeneity-induced cosmic acceleration in a dust universe
It is the common consensus that the expansion of a universe always slows down if the gravity provided by the energy sources therein is attractive and accordingly one needs to invoke dark energy as a
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
Backreaction of cosmological perturbations in covariant macroscopic gravity
The problem of corrections to Einstein's equations arising from averaging of inhomogeneities (backreaction) in the cosmological context has gained considerable attention recently. We present results
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There is an ongoing debate in the literature as to whether the effects of averaging out inhomogeneities ('backreaction') in cosmology can be large enough to account for the acceleration of the scale
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
Post-Newtonian cosmological dynamics of plane-parallel perturbations and back-reaction
We study the general relativistic non-linear dynamics of self-gravitating ir- rotational dust in a cosmological setting, adopting the comoving and synchronous gauge, where all the equations can be


Back reaction and local cosmological expansion rate
We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. Specifically, we consider a cosmological model
Relativistic second-order perturbations of the Einstein-de Sitter Universe
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While the expansion rate of a homogeneous isotropic universe is simply proportional to the square-root of the energy density, the expansion rate of an inhomogeneous universe also depends on the
Post-Newtonian Cosmological Dynamics in Lagrangian coordinates
We study the non-linear dynamics of self-gravitating irrotational dust in a general relativistic framework, using synchronous and comoving (i.e. Lagrangian) coordinates. All the equations are written
The 4 Year COBE Normalization and Large-Scale Structure
We present an analysis of the 4 year data from the COBE DMR experiment. We use a Karhunen- Loeve expansion of the pixel data to calculate the normalization and goodness of -t of a range of models of
First year Wilkinson Microwave Anisotropy Probe (WMAP) observations: Determination of cosmological parameters
WMAP precision data enable accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat � -dominated universe seeded by a nearly scale-invariant adiabatic
The statistics of peaks of Gaussian random fields
A set of new mathematical results on the theory of Gaussian random fields is presented, and the application of such calculations in cosmology to treat questions of structure formation from
The Four-Year COBE Normalization and Large-Scale Structure
  • 1996