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:
“When I from black and he from white cloud free,
And round the tent of Godlike lambs we joy,
I’ll shade him from the heat till he can bear
To lean in joy upon our father’s knee;
And then I’ll stand and stroke his silver hair,
And be like him, and he will then love me.”
—William Blake (1757–1827)
“Angel of hope and calendars, do you know despair?
That hole I crawl into with a box of Kleenex....”
—Anne Sexton (1928–1974)