In
theoretical physics, a near-extremal black hole is a
black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
which is not far from the minimal possible mass that can be compatible with the given
charges and
angular momentum. The calculations of the properties of near-extremal black holes are usually performed using
perturbation theory around the
extremal black hole; the expansion parameter is called non-extremality.
In
supersymmetric
In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories ...
theories, near-extremal black holes are often small perturbations of supersymmetric black holes. Such black holes have a very small
Hawking temperature and consequently emit a small amount of
Hawking radiation. Their
black hole entropy can often be calculated in
string theory
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and interac ...
, much like in the case of extremal black holes, at least to the first order in non-extremality.
Black holes
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