The structure and properties of asymptotically shear-free NGCs (our main topic) are best understood by
first looking at the special case of congruences that are shear-free everywhere (except at their caustics).
Though shear-free congruences are also found in algebraically-special spacetimes, in this section only the
shear-free NGCs in Minkowski spacetime, , are discussed [7
]
http://www.livingreviews.org/lrr-2012-1 |
Living Rev. Relativity 15, (2012), 1
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