General Relativity
CTCs appear in locally unobjectionable exact solutions to the Einstein field equation of general relativity, including some of the most important solutions. These include:
- the Misner space (which is Minkowski space orbifolded by a discrete boost)
- the Kerr vacuum (which models a rotating uncharged black hole)
- the interior of a rotating BTZ black hole
- the van Stockum dust (which models a cylindrically symmetric configuration of dust)
- the Gödel lambdadust (which models a dust with a carefully chosen cosmological constant term)
- the Tipler cylinder (a cylindrically symmetric metric with CTCs)
- Bonnor Steadman solutions describing laboratory situations such as two spinning balls
- J. Richard Gott has proposed a mechanism for creating CTCs using cosmic strings.
Some of these examples are, like the Tipler cylinder, rather artificial, but the exterior part of the Kerr solution is thought to be in some sense generic, so it is rather unnerving to learn that its interior contains CTCs. Most physicists feel that CTCs in such solutions are artifacts.
Read more about this topic: Closed Timelike Curve
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