Cosmological backreaction and its dependence on spacetime foliation. (13th November 2018)

• Record Type: Journal Article
• Authors: Buchert, Thomas; Mourier, Pierre; Roy, Xavier
• Is Part Of: Classical and quantum gravity. Volume 35:Number 24(2018:Dec.)
• Publication Date: 2018-11-13
• Subjects: cosmology -- foliations -- Lagrangian description -- backreaction; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/1361-6382/aaebce
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: The subject of cosmological backreaction in general relativity is often approached by coordinate-dependent and metric-based analyses. We present in this letter an averaging formalism for the scalar parts of Einstein's equations that is coordinate-independent and only functionally depends on a metric. This formalism is applicable to general 3 + 1 foliations of spacetime for an arbitrary fluid with tilted flow. We clarify the dependence on spacetime foliation and argue that this dependence is weak in cosmological settings. We also introduce a new set of averaged equations that feature a global cosmological time despite the generality of the setting, and we put the statistical nature of effective cosmologies into perspective.