Is there proof that backreaction of inhomogeneities is irrelevant in cosmology?

Buchert, Thomas; Carfora, Mauro; Ellis, George; Kolb, Edward W.; MacCallum, Malcolm; Ostrowski, Jan J.; Räsänen, Syksy; Roukema, Boudewijn F.; Andersson, Lars; Coley, A. A.; Wiltshire, David L.

doi:10.1088/0264-9381/32/21/215021

Cited by 173 publications

(248 citation statements)

References 138 publications

(392 reference statements)

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“…Therefore, also, this indication of dark energy is metrology dependent! Let us also remark that in the back-reaction approach [64][65][66][67][68][69], in which to take into account the inhomogeneity of the observed universe when trying to get a cosmological description of it, one considers spatial mean values on large scales, dark energy in cosmology is a byproduct of the nonlinearities of GR. In this approach, one gets that the spatial average of the 4-scalar gauge variable York time gives the effective Hubble constant of this approach.…”

Section: Trends In Modern Cosmologymentioning

confidence: 99%

Relativistic Celestial Metrology: Dark Matter as an Inertial Gauge Effect

Lusanna¹,

Stanga²

2017

Trends in Modern Cosmology

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In canonical tetrad gravity, it is possible to identify the gauge variables, describing relativistic inertial effects, in Einstein general relativity. One of these is the York time, the trace of the extrinsic curvature of the instantaneous non-Euclidean 3-spaces (global Euclidean 3-spaces are forbidden by the equivalence principle). The extrinsic curvature depends both on gauge variables and on dynamical ones like the gravitational waves after linearization. The fixation of these gauge variables is done by relativistic metrology with its identification of time and space. Till now, the International Celestial Reference Frame ICRF uses Euclidean 3-spaces outside the Solar System. It is shown that York time and non-Euclidean 3-spaces may explain the main signatures of dark matter in ordinary space-time before using cosmology. Also dark energy may be connected to these inertial gauge effects, because both red-shift and luminosity distance depend on them.

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Section: Trends In Modern Cosmologymentioning

confidence: 99%

Relativistic Celestial Metrology: Dark Matter as an Inertial Gauge Effect

Lusanna¹,

Stanga²

2017

Trends in Modern Cosmology

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“…It is noteworthy that, there have been numerous attempts to vet and prove a modification [12] for the Friedman Walker cosmology, which has been correction to the large scale inhomogeneity raised as a possibility by [13]- [17], as the approach taken by Wald, and Green, a summary can be seen in the statement that as given by [14] We have the situation in defining…”

Section: The Questions Of Nonstandard Cosmologies Before Delving Intmentioning

confidence: 99%

Gedanken Experiment for Degree of Flatness, or Lack of, in Early Universe Conditions

Beckwith¹

2016

JHEPGC

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This document will from first principles delineate the degree of flatness, or deviations from, in early universe models. We will, afterwards, make comparison with recent results we have looked at concerning metric tensor fluctuations and comment upon the role of what early universe gravitational energy may play a role in the presumed deviation from flat space results. Note that ( ) 37 initial gravitoñ~1 0 N S will be tied into the presumed results for initial state density, in ways we will comment upon, leading to observations which are supporting the physics given by Equation (26) of this document as with regards to Gravitational waves, from relic conditions. The deviations from flat space may help confirm the conclusions given by Buchert, Carfora, Kolb, and Wiltshire allegedly refuting the claim by Green and Wald that "the standard FLRW model approximates our Universe extremely well on all scales, except close to strong field astrophysical objects", as well as give additional analysis appropriate for adding detail to expanding experimental procedures for investigating non FLRW models such as the Polynomial Inflation models as given by Kobayashi, and Seto, as well as other nonstandard cosmologies, as brought up by Corda, and other researchers. As well as improve upon post Bicep 2 measurements which will avoid GW signatures from interstellar dust, as opposed to relic GW. We hope that our approach may help in the differentiation between different cosmology models. Most importantly, our procedure may help, with refinement of admissible frequency range, avoid the problem of BICEP 2, which had its presumed GW signals from presumed relic conditions identical to dust induced frequencies, as so identified by the Planck collaboration in reference [25] which we comment upon in the conclusion.

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“…Also, Green and Wald have found in [21] that within their formalism the effect of small-scale inhomogeneities on the long wavelength perturbations is to add extra terms to the perturbed stress energy which they state corresponds to what one would expect from kinetic motions, and Newtonian potential energy and stresses. Buchert et al [26] objected that Green and Wald formalism is not general enough to capture generic properties of a realistic backreaction. They also pointed out that some assumptions have discarded important points in the fitting and averaging problem, by construction.…”

Section: Parametersmentioning

confidence: 99%

“…They also pointed out that some assumptions have discarded important points in the fitting and averaging problem, by construction. Green and Wald responded [27] to the criticism stating that their results remain valid and that there are various ways to define what backreaction is, which was in turn described again to be limited by [26]. They finally proposed a heurestic description in [28] to justify their previous results.…”

Section: Parametersmentioning

confidence: 99%

Averaged universe confronted with cosmological observations: A fully covariant approach

2016

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One of the outstanding problems in general relativistic cosmology is that of the averaging. That is, how the lumpy universe that we observe at small scales averages out to a smooth FriedmannLemaitre-Robertson-Walker (FLRW) model. The root of the problem is that averaging does not commute with the Einstein equations that govern the dynamics of the model. This leads to the well-know question of backreaction in cosmology. In this work, we approach the problem using the covariant framework of Macroscopic Gravity (MG). We use its cosmological solution with a flat FLRW macroscopic background where the result of averaging cosmic inhomogeneities has been encapsulated into a backreaction density parameter denoted ΩA. We constrain this averaged universe using available cosmological data sets of expansion and growth including, for the first time, a full CMB analysis from Planck temperature anisotropy and polarization data, the supernovae data from Union 2.1, the galaxy power spectrum from WiggleZ, the weak lensing tomography shear-shear cross correlations from the CFHTLenS survey and the baryonic acoustic oscillation data from 6Df, SDSS DR7 and BOSS DR9. We find that −0.0155 ≤ ΩA ≤ 0 (at the 68% CL) thus providing a tight upper-bound on the backreaction term. We also find that the term is strongly correlated with cosmological parameters such ΩΛ, σ8 and H0. While small, a backreaction density parameter of a few percent should be kept in consideration along with other systematics for precision cosmology.PACS numbers: 98.80. Es,95.30.Sf

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Is there proof that backreaction of inhomogeneities is irrelevant in cosmology?

Cited by 173 publications

References 138 publications

Relativistic Celestial Metrology: Dark Matter as an Inertial Gauge Effect

Relativistic Celestial Metrology: Dark Matter as an Inertial Gauge Effect

Gedanken Experiment for Degree of Flatness, or Lack of, in Early Universe Conditions

Averaged universe confronted with cosmological observations: A fully covariant approach

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