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:
“Just like those other black holes from outer space, Hollywood is postmodern to this extent: it has no center, only a spreading dead zone of exhaustion, inertia, and brilliant decay.”
—Arthur Kroker (b. 1945)
“It’s perversion. Don’t you see what it is? It’s not natural. To go to great expense for something you want, that’s natural. To reach out to take it, that’s human, that’s natural. But to get your pleasure from not taking, from cheating yourself deliberately like my brother did today, from not getting, from not taking. Don’t you see what a black thing that is for a man to do? How it is to hate yourself?”
—Abraham Polonsky (b. 1910)
“The cosmos is about the smallest hole that a man can hide his head in.”
—Gilbert Keith Chesterton (1874–1936)