Mass formula for Kerr black holes
L. Smarr, Physical Review Letters, 30, 71-73 (1973).
Abstract
A new mass formula for Kerr black holes is deduced and is contrasted to the mass formula which is obtained by integrating term by term the mass differential and which consists of three terms interpreted, respectively, as the surface energy, rotational energy, and electromagnetic energy of the charged rotating black hole. A comparison is suggested between a rotating black hole and a rotating liquid drop which leads to a speculation that Kerr black holes may develop instabilities.