Cosmological backreaction and its dependence on spacetime foliation

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