Explicit cosmological coarse graining via spatial averaging
TLDR
In this paper, the evolution of the scale factor in such a construction must be governed not by the standard Einstein equations for the FLRW metric, but by the modified Friedmann equations derived by Buchert (Gen Relat Gravit 32:105, 2000; 33:1381, 2001).Abstract:
The present matter density of the Universe, while highly inhomogeneous on small scales, displays approximate homogeneity on large scales. We propose that whereas it is justified to use the Friedmann–Lemaitre–Robertson–Walker (FLRW) line element (which describes an exactly homogeneous and isotropic universe) as a template to construct luminosity distances in order to compare observations with theory, the evolution of the scale factor in such a construction must be governed not by the standard Einstein equations for the FLRW metric, but by the modified Friedmann equations derived by Buchert (Gen Relat Gravit 32:105, 2000; 33:1381, 2001) in the context of spatial averaging in Cosmology. Furthermore, we argue that this scale factor, defined in the spatially averaged cosmology, will correspond to the effective FLRW metric provided the size of the averaging domain coincides with the scale at which cosmological homogeneity arises. This allows us, in principle, to compare predictions of a spatially averaged cosmology with observations, in the standard manner, for instance by computing the luminosity distance versus red-shift relation. The predictions of the spatially averaged cosmology would in general differ from standard FLRW cosmology, because the scale-factor now obeys the modified FLRW equations. This could help determine, by comparing with observations, whether or not cosmological inhomogeneities are an alternative explanation for the observed cosmic acceleration.read more
Citations
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Cosmological non-linearities as an effective fluid
TL;DR: In this article, the authors show that the long-wavelength universe behaves as a viscous fluid coupled to gravity, and that the backreaction of small-scale nonlinearities is very small, being suppressed by the large hierarchy between the scale of non-linearities and the horizon scale.
Journal ArticleDOI
Dark Energy from structure: a status report
Thomas Buchert,Thomas Buchert +1 more
TL;DR: In this paper, the authors provide an overview over the Dark Energy debate in connection with the impact of inhomogeneities, and formulates strategies for a comprehensive quantitative evaluation of backreaction effects both in theoretical and observational cosmology.
Journal ArticleDOI
Is there proof that backreaction of inhomogeneities is irrelevant in cosmology
Thomas Buchert,Mauro Carfora,Mauro Carfora,George F. R. Ellis,Edward W. Kolb,Malcolm MacCallum,Jan J. Ostrowski,Jan J. Ostrowski,Syksy Räsänen,Boudewijn F. Roukema,Boudewijn F. Roukema,Lars Andersson,Alan Coley,David L. Wiltshire +13 more
TL;DR: The trace-free property of backreaction in cosmology was shown to be unphysical in this paper, and the scheme that underlies the trace free theorem does not involve averaging and therefore does not capture crucial non-local effects.
Journal ArticleDOI
Does the growth of structure affect our dynamical models of the Universe? The averaging, backreaction, and fitting problems in cosmology
TL;DR: In this article, it was shown that the process of smoothing over structure can contribute to an acceleration term and so alter the apparent value of the cosmological constant, and that concordance cosmology may be affected by back-reaction effects.
References
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Measurements of Omega and Lambda from 42 High-Redshift Supernovae
Saul Perlmutter,Saul Perlmutter,Greg Aldering,Gerson Goldhaber,Gerson Goldhaber,R. A. Knop,Peter Nugent,P. G. Castro,P. G. Castro,Susana E. Deustua,Sebastien Fabbro,Sebastien Fabbro,A. Goobar,A. Goobar,Donald E. Groom,I. M. Hook,I. M. Hook,A. G. Kim,A. G. Kim,A. G. Kim,M. Y. Kim,Julia C. Lee,Julia C. Lee,Nelson J. Nunes,Nelson J. Nunes,Reynald Pain,Reynald Pain,C. R. Pennypacker,C. R. Pennypacker,Robert Quimby,Christopher Lidman,Richard S. Ellis,Mike Irwin,Richard G. McMahon,Pilar Ruiz-Lapuente,Nicholas A. Walton,Bradley E. Schaefer,B. J. Boyle,Alexei V. Filippenko,Thomas Matheson,A. S. Fruchter,Nino Panagia,Nino Panagia,Heidi Jo Newberg,Warrick J. Couch +44 more
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured using the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology project.
Journal ArticleDOI
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
Adam G. Riess,Alexei V. Filippenko,Peter Challis,Alejandro Clocchiatti,Alan H. Diercks,Peter M. Garnavich,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,Mark M. Phillips,David J Reiss,Brian P. Schmidt,R. A. Schommer,R. Chris Smith,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +20 more
TL;DR: In this article, the authors used spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62.
Journal ArticleDOI
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
Adam G. Riess,Alexei V. Filippenko,Peter Challis,Alejandro Clocchiattia,Alan H. Diercks,Peter M. Garnavich,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,Mark M. Phillips,David J Reiss,Brian P. Schmidt,Robert A. Schommer,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +19 more
TL;DR: In this paper, the authors present observations of 10 type Ia supernovae (SNe Ia) between 0.16 0 and 4.0 sigma confidence levels, for two fitting methods respectively.
Journal ArticleDOI
Measurements of Omega and Lambda from 42 High-Redshift Supernovae
Saul Perlmutter,Greg Aldering,G. Goldhaber,R. A. Knop,Peter Nugent,P. G. Castro,Susana E. Deustua,Sebastien Fabbro,A. Goobar,D. E. Groom,I. M. Hook,A. G. Kim,M. Y. Kim,Julia C. Lee,Nelson J. Nunes,Reynald Pain,C. R. Pennypacker,R. M. Quimby,C. Lidman,Richard S. Ellis,Michael G. Irwin,Richard G. McMahon,P. Ruiz-Lapuente,Nicholas A. Walton,Bradley E. Schaefer,B. J. Boyle,Alexei V. Filippenko,Thomas Matheson,A. S. Fruchter,Nino Panagia,Heidi Jo Newberg,W. J. Couch +31 more
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured by the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project.
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant To Appear in the Astronomical Journal
Adam G. Riess,Alexei V. Filippenko,Peter Challis,A. Clocchiatti,Alan H. Diercks,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,David J Reiss,Brian P. Schmidt,Robert A. Schommer,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +17 more
TL;DR: The spectral and photometric observations of 10 type Ia supernovae (SNe Ia) in the redshift range 0.16 � z � 0.62 were presented in this paper.
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