On Average Properties of Inhomogeneous Fluids in General Relativity: Perfect Fluid Cosmologies

By T. Buchert. 2001

351 citations recorded by the source corpus.

For general relativistic spacetimes filled with an irrotational perfect fluid a generalized form of Friedmann's equations governing the expansion factor of spatially averaged portions of inhomogeneous cosmologies is derived. The averaging problem for scalar quantities is condensed into the problem of finding an "effective equation of state" including kinematical as well as dynamical "backreaction" terms that measure the departure from a standard FLRW cosmology. Applications of the averaged models are outlined including radiation-dominated and scalar field cosmologies (inflationary and dilaton/string cosmologies). In particular, the averaged equations show that the averaged scalar curvature must generically change in the course of structure formation, that an averaged inhomogeneous radiation cosmos does not follow the evolution of the standard homogeneous-isotropic model, and that an averaged inhomogeneous perfect fluid features kinematical "backreaction" terms that, in some cases, act like a free scalar field source. The free scalar field (dilaton) itself, modelled by a "stiff" fluid, is singled out as a special inhomogeneous case where the averaged equations assume a simple form.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/2bfacfd8c41de96de58fd0fc27960ea6f46d9d95

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In Astronomy and Astrophysics

In Nuclear and High Energy Physics

In Statistical and Nonlinear Physics

Citations in the corpus

Backreaction in Late-Time Cosmology (2011, background): “For discussion of non-dust matter, see [41–44].”
Dark Energy from structure: a status report (2007, methodology): “where we have written the local coordinates in capital lette rs now, as in the main text, to indicate that they now label comoving fluid elements . 50 We here recall the results given in [ 34 ].”