nLab
black hole

Context

Gravity

Physics

physics, mathematical physics, philosophy of physics

Surveys, textbooks and lecture notes


theory (physics), model (physics)

experiment, measurement, computable physics

Contents

Idea

A black hole is a spacetime that solves Einstein equations of general relativity characterized by the fact that it possesses an event horizon hypersurface (or several of them) which has a number of special characteristics, for example that light cannot escape from the space confined by the horizon hypersurface due to gravitational effects. Much of the theoretical considerations are about the entropy of black holes (cf. Bekenstein-Hawking entropy) and the information paradox.

Black holes are considered theoretically for gravitational theories in various number dd of dimension. For d5d \geq 5 a black hole spacetime may have nontrivial topology, e.g. black rings are possible.

Examples

Properties

Topology

Hawking’s Theorem of Black Hole topology asserts that the in case of d=4d = 4 asymptotically flat stationary black holes satisfying the suitable dominant energy condition, the cross sections of the event horizon are spherical.

Galloway and Schoen extended this theorem to higher dimensions; they showed that the cross sections of event horizon (stationary case) and the outer (apparent) horizon (general case) are of Yamabe type.

Entropy

Empirical observation

See

Some candidate astrophysical? objects which seem to point to black hole have been observed.

Examples

black hole spacetimesvanishing angular momentumpositive angular momentum
vanishing chargeSchwarzschild spacetimeKerr spacetime
positive chargeReissner-Nordstrom spacetimeKerr-Newman spacetime

\,

References

Observation

Resolved image of the direct vicinity of the event horizon of the black hole in the center of the galaxy Messier 87:

Review

In supergravity

Black holes in supergravity:

Holographic description

Discussion of black holes in the context of the holographic principle and the AdS-CFT correspondence is in

The nature of the event horizon, specifically, is discussed in

Cosmology inside black holes