Evaluating backreaction with the peak model of structure formation

Räsänen, Syksy

doi:10.1088/1475-7516/2008/04/026

Cited by 84 publications

(183 citation statements)

References 254 publications

(357 reference statements)

Supporting

Mentioning

174

Contrasting

Order By: Relevance

“…Another improvement will come from a closure condition that is better than a simple scaling solution, and that will encode more precisely the time evolution of backreaction. Such a closure condition can be looked for in numerical simulations, analytical approximations (see [73,74,75] for particular approximations, and [76,77,78] for an interesting perspective), or observations (see [79] and references therein for remarks on the difficulties of this last approach). Moreover, the complete study of other observables like the full CMB spectrum is still unavailable and will be crucial for the construction and the test of a 'concordance model' for averaged inhomogeneous cosmologies.…”

Section: Discussionmentioning

confidence: 99%

Testing backreaction effects with observations

et al. 2009

View full text Add to dashboard Cite

Abstract. In order to quantitatively test the ability of averaged inhomogeneous cosmologies to correctly describe observations of the large scale properties of the Universe, we introduce a smoothed template metric corresponding to a constant spatial curvature model at any time, but with an evolving curvature parameter. This metric is used to compute quantities along an approximate effective lightcone of the averaged model of the Universe. As opposed to the standard Friedmann model, we parameterize this template metric by exact scaling properties of an averaged inhomogeneous cosmology, and we also motivate this form of the metric by results on a geometrical smoothing of inhomogeneous cosmological hypersurfaces. The purpose of the paper is not to demonstrate that the backreaction effect is actually responsible for the Dark Energy phenomenon by explicitly calculating the effect from a local model of the geometry and the distribution of matter, but rather to propose a way to deal with observations in the backreaction context, and to understand what kind of generic properties have to hold in order for a backreaction model to explain the observed features of the Universe on large scales. We test our hypothesis for the template metric against supernova data and the position of the CMB peaks, and infer the goodness-of-fit and parameter uncertainties. We find that averaged inhomogeneous models can reproduce the observations without requiring an additional Dark Energy component (though a volume acceleration is still needed), and that current data do not disfavour our main assumption on the effective lightcone structure. We also show that the experimental uncertainties on the angular diameter distance and the Hubble parameter from Baryon Acoustic Oscillations measurements -forseen in future surveys like the proposed EUCLID satellite project -are sufficiently small to distinguish between a FLRW template geometry and the template geometry with consistently evolving curvature.

show abstract

Section: Discussionmentioning

confidence: 99%

Testing backreaction effects with observations

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Another definition of acceleration, as dubbed "domain acceleration" in the present paper, has been widely used in the literature [11,21,35,36,37,42,49,50,51,52,53,54]. It is for a spatial domain D with a finite volume…”

Section: B Domain Accelerationmentioning

confidence: 99%

“…One may treat a complicated universe as a large domain consisting of many different sub-domains, and from a statistical perspective it might be reasonable that the size L D of the large domain corresponds to the scale factor in the FRW metric. In many works the results from the analysis involving the quantity L D are compared with observations in this spirit [36,37,42,50,51,60]. Nevertheless, whether this is a good approximation is not clear yet.…”

Section: Domain Acceleration Induced By Inhomogeneitiesmentioning

confidence: 99%

Inhomogeneity-induced cosmic acceleration in a dust universe

Chuang

Gu²,

Hwang

2008

Class. Quantum Grav.

View full text Add to dashboard Cite

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 source of anti-gravity for understanding the cosmic acceleration. To examine this point we find counter-examples for a spherically symmetric dust fluid described by the Lemaitre-TolmanBondi solution without singularity. Thus, the validity of this naive consensus is indeed doubtful and the effects of inhomogeneities should be restudied. These counter-intuitive examples open a new perspective on the understanding of the evolution of our universe.

show abstract

“…pec_expan-bbl tions of emerging average negative curvature models, include, e.g., toy models of collapsing and expanding spheres (Räsänen 2006) or Lemaître-Tolman-Bondi (LTB) regions (Nambu & Tanimoto 2005;Kai et al 2007), a peak model (Räsänen 2008), a metric template model (Larena et al 2009;Chiesa et al 2014), bi-scale or more general multi-scale models (Wiegand & Buchert 2010;Buchert & Räsänen 2012), the Timescape model (Wiltshire 2009;Duley, Nazer, & Wiltshire 2013;Nazer & Wiltshire 2015), the virialisation approximation (Roukema, Ostrowski, & Buchert 2013), an effective viscous pressure approach , and Swiss cheese models that paste exact inhomogeneous solutions into holes in a homogeneous (FLRW) background (Bolejko & Célérier 2010; the Tardis model of Lavinto, Räsänen, & Szybka 2013). Updates to many of these models should benefit from an observationally justified estimate of H bg 1 .…”

Section: Introductionmentioning

confidence: 99%

The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe

Roukema

Mourier

Buchert

et al. 2017

A&A

View full text Add to dashboard Cite

Context. In relativistic inhomogeneous cosmology, structure formation couples to average cosmological expansion. A conservative approach to modelling this assumes an Einstein-de Sitter model (EdS) at early times and extrapolates this forward in cosmological time as a "background model" against which average properties of today's Universe can be measured. Aims. This requires adopting an early-epoch-normalised background Hubble constant H bg 1 .Methods. Here, we show that the ΛCDM model can be used as an observational proxy to estimate H bg 1 rather than choose it arbitrarily. We assume (i) an EdS model at early times; (ii) a zero dark energy parameter; (iii) bi-domain scalar averaging-division of the spatial sections into over-and underdense regions; and (iv) virialisation (stable clustering) of collapsed regions. Results. We find H bg 1 = 37.7 ± 0.4 km/s/Mpc (random error only) based on a Planck ΛCDM observational proxy. Conclusions. Moreover, since the scalar-averaged expansion rate is expected to exceed the (extrapolated) background expansion rate, the expected age of the Universe should be much less than 2/(3H bg 1 ) = 17.3 Gyr. The maximum stellar age of Galactic Bulge microlensed low-mass stars (most likely: 14.7 Gyr; 68% confidence: 14.0-15.0 Gyr) suggests an age about a Gyr older than the (no-backreaction) ΛCDM estimate.

show abstract

Evaluating backreaction with the peak model of structure formation

Cited by 84 publications

References 254 publications

Testing backreaction effects with observations

Testing backreaction effects with observations

Inhomogeneity-induced cosmic acceleration in a dust universe

The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe

Contact Info

Product

Resources

About