black hole spacetimes | vanishing angular momentum | positive angular momentum |
---|---|---|
vanishing charge | Schwarzschild spacetime | Kerr spacetime |
positive charge | Reissner-Nordstrom spacetime | Kerr-Newman spacetime |
The cosmic censorship hypothesis is the name of a pair of conjectures (Penrose 69) saying that in the theory of general relativity, under physically reasonable conditions, any singularities in spacetime must lie behind an event horizon.
Both the weak and the string form of the conjecture concern solutions of Einstein's equations with physically realistic matter and generic compact or asymptotically flat initial data.
The strong cosmic censorship conjecture, proposed by Penrose in 1986, states that the maximal Cauchy development of such a solution is locally inextendible as a regular Lorentzian manifold.
The weak cosmic censorship hypothesis, proposed by him in 1988, asserts that for generic initial data, the maximal Cauchy development of a solution of Einstein’s equations with realistic matter possesses a complete future null infinity.
Despite their names, the strong version does not necessarily imply the weak version.
Without the ‘genericity’ condition, which needs to be carefully stated, both strong and weak cosmic censorship fail. That is, with carefully fine-tuned initial data one can find counterexamples.
The weak cosmic censorship conjecture has many counterexamples in dimension $d \geq 5$. Cumrun Vafa has argued that the weak gravity conjecture will save the cosmic censorship conjecture. The weak gravity conjecture says that in consistent theories of quantum gravity the gravitational force exerted by any object (e.g. a black hole) has to be weaker, in suitable units, than any other force. As discussed in (Crisford-Santos 17) it seems plausible that this constraint would indeed rule out the counterexample constructed there:
Subsequent calculations by Santos and Crisford supported Vafa’s hunch; the simulations they’re running now could verify that naked singularities become cloaked in black holes right at the point where gravity becomes the weakest force. (Wolchover, June 20 2017)
The weak gravity conjecture was motivated from string theory, where there are various plausibility arguments that it holds.
The original article:
Review:
Roger Penrose, The Question of Cosmic Censorship, Journal of Astrophysics and Astronomy, Vol. 20, p.233, 1999 (doi:10.1007/BF02702355, web)
Klaas Landsman, Singularities, black holes, and cosmic censorship: A tribute to Roger Penrose (arXiv:2101.02687)
See also:
For strong cosmic censorship, see:
In 2017 Dafermos and Luk found a counterexample to strong cosmic censorship without the requirement that the initial data be generic:
Discussion in relation to computability in physics and Malament–Hogarth spacetimes:
In 2020, Hod claimed a “remarkably compact proof” of strong cosmic censorship:
Review of weak cosmic censorship:
In 1993 Choptuik found a counterexample to weak cosmic censorship without the requirement that the initial data be generic, by considering a spherically symmetric solution of gravity coupled to a scalar field right on the brink of the formation of a black hole. This and subsequent work is reviewed here:
For a proof of weak cosmic censorship in the spherically symmetric case, see:
A counterexample in 4-dimensional anti-de Sitter spacetime:
A counterexample in 6-dimensional spacetime:
For BTZ black holes:
Relation to the weak gravity conjecture:
Relation to higher curvature corrections:
Last revised on April 21, 2021 at 23:56:33. See the history of this page for a list of all contributions to it.