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 hole, black and/or hole:
“The shadow of the Venetian blind on the painted wall,
Shadows of the snake-plant and cacti, the plaster animals,
Focus the tragic melancholy of the bright stare
Into nowhere, a hole like the black holes in space.”
—John Ashbery (b. 1927)
“Know that, on the right hand of the Indies, there is an island called California, very near to the Terrestrial Paradise, which was peopled with black women.... Their arms were all of gold.”
—For the State of California, U.S. public relief program (1935-1943)
“The cosmos is about the smallest hole that a man can hide his head in.”
—Gilbert Keith Chesterton (1874–1936)