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:
“Some burn damp faggots, others may consume
The entire combustible world in one small room
As though dried straw, and if we turn about
The bare chimney is gone black out
Because the work had finished in that flare.”
—William Butler Yeats (1865–1939)
“During Prohibition days, when South Carolina was actively advertising the iodine content of its vegetables, the Hell Hole brand of ‘liquid corn’ was notorious with its waggish slogan: ‘Not a Goiter in a Gallon.’”
—Administration in the State of Sout, U.S. public relief program (1935-1943)