no-hair theorem

The no-hair theorem is the proposition that a black hole's state (that effects its interaction with the rest of the universe) consists only of its mass, rotation, and electric charge (other than its position, velocity, and the attitude of its rotation axis), no other qualities independent of these having any such effect. The word hair is used metaphorically for any other qualities. A proof of the proposition would rest on the correctness of a substantial amount of physics, e.g., perhaps it will prove to follow from general relativity. To date, proofs have been accomplished only regarding some black hole models. Presumption of its general correctness is the conventional view of black holes but interest remains in proofs/disproofs/counter-examples. Data from GW detections are claimed to be consistent with the proposition. The implication of the theorem is that two black holes that are the same regarding those three values interact with us identically, even, for example, if one was formed of matter and the other antimatter.