Maciej Dunajski and Gary Gibbons 2008 Class. Quantum Grav. 25 235012 doi:10.1088/0264-9381/25/23/235012
Maciej Dunajski and Gary Gibbons
Show affiliationsWe clarify the procedure for expressing the Friedmann equation in terms of directly measurable cosmological scalars constructed out of higher derivatives of the scale factor. We carry out this procedure for pure dust, Chaplygin gas and generalized Chaplygin gas energy–momentum tensors. In each case it leads to a constraint on the scalars thus giving rise to a test of general relativity. We also discuss a formulation of the Friedmann equation as unparametrized geodesic motion and its connection with the Lagrangian treatment of perfect fluids coupled to gravity.
95.30.Sf Relativity and gravitation
04.40.Nr Einstein-Maxwell spacetimes, spacetimes with fluids, radiation or classical fields
Issue 23 (7 December 2008)
Received 8 July 2008, in final form 11 September 2008
Published 17 November 2008
Maciej Dunajski and Gary Gibbons 2008 Class. Quantum Grav. 25 235012
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