In theoretical physics, a near-extremal black hole is a black hole 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 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, much like in the case of extremal black holes, at least to the first order in non-extremality.
Famous quotes containing the words black and/or hole:
“... burned to tireless death
A child of a few hours
With its kneading mouth
Charred on the black breast of the grave
The mother dug, and its arms full of fires ...”
—Dylan Thomas (1914–1953)
“The cosmos is about the smallest hole that a man can hide his head in.”
—Gilbert Keith Chesterton (1874–1936)