Dark Energy from structure: a status report

By T. Buchert. 2007

406 citations recorded by the source corpus.

The effective evolution of an inhomogeneous universe model in any theory of gravitation may be described in terms of spatially averaged variables. In Einstein’s theory, restricting attention to scalar variables, this evolution can be modeled by solutions of a set of Friedmann equations for an effective volume scale factor, with matter and backreaction source terms. The latter can be represented by an effective scalar field (“morphon field”) modeling Dark Energy. The present work provides 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. We recall the basic steps of a description of backreaction effects in relativistic cosmology that lead to refurnishing the standard cosmological equations, but also lay down a number of challenges and unresolved issues in connection with their observational interpretation. The present status of this subject is intermediate: we have a good qualitative understanding of backreaction effects pointing to a global instability of the standard model of cosmology; exact solutions and perturbative results modeling this instability lie in the right sector to explain Dark Energy from inhomogeneities. It is fair to say that, even if backreaction effects turn out to be less important than anticipated by some researchers, the concordance high-precision cosmology, the architecture of current N-body simulations, as well as standard perturbative approaches may all fall short in correctly describing the Late Universe.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d826f26fa8c8bcd70f5e11e161760d9be658c3ff

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Citations in the corpus

Cosmology and Fundamental Physics with the Euclid Satellite (2012, methodology): “One ansatz tries to construct average quantities that follow equations similar to those of the traditional FLRW model, see [249, 250].”
Backreaction in Late-Time Cosmology (2011, background): “Note that in the presence of inhomogeneities the averaged scalar curvature does not obey a separate conservation law as the density does (unlike in FLRW cosmology): only a combination of the average spatial curvature and the kinematical backreaction variable is conserved [9].”
Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, neutral): “, [84, 488, 489].”
Influence of global cosmological expansion on local dynamics and kinematics (2008, background): “a context with realistic inhomogeneities (Buchert, 2000; Ra¨s¨anen, 2006; Wiltshire, 2007), i.e. taking into account that cosmological param31 eters are dressed (Buchert and Carfora, 2003). See also (Buchert, 2008) for a recent review. One might speculate that the measured Λ can eventually be fully ”
The WiggleZ Dark Energy Survey: the transition to large-scale cosmic homogeneity (2012, background): “If we assume that GR holds, but take inhomogeneities into account, it can be shown that backreaction can cause a global cosmic acceler- ation, without any additional dark energy component (see e.g. Schwarz 2002; Kolb et al. 2005; Räsänen 2006; Wiltshire 2007a; Buchert 2008; Räsänen 2011).”