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gr-qc2009★ 34 cited
Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
Thomas Buchert, George F R Ellis, Henk van Elst
The thoughts expressed in this article are based on remarks made by Jürgen Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main objective of this article is…
gr-qc2008
On the Flow of Time
George F R Ellis
Current theoretical physics suggests the flow of time is an illusion: the entire universe just is, with no special meaning attached to the present time. This paper points out that…
gr-qc2006★ 1 cited
Group classification of the Sachs equations for a radiating axisymmetric, non-rotating, vacuum space-time
Nail H. Ibragimov, Ewald J. H. Wessels, George F. R. Ellis
We carry out a Lie group analysis of the Sachs equations for a time-dependent axisymmetric non-rotating space-time in which the Ricci tensor vanishes. These equations, which are th…