Black holes are characterized only by mass, charge, and spin
The no-hair theorem states that all stationary black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three independent externally observable classical parameters: mass, electric charge, and angular momentum.
Other characteristics are uniquely determined by these three parameters, and all other information about the matter that formed a black hole or is falling into it disappears behind the black-hole event horizon and is therefore permanently inaccessible to external observers after the black hole settles down.
Physicist John Archibald Wheeler expressed this idea with the phrase black holes have no hair, which was the origin of the name.
Constraints on possible particle properties
In theoretical physics, the Weinberg–Witten (WW) theorem, proved by Steven Weinberg and Edward Witten, states that massless particles (either composite or elementary) with spin j > 1/2 cannot carry a
Lorentz-covariant current, while massless particles with spin j > 1 cannot carry a Lorentz-covariant stress-energy.
The theorem is usually interpreted to mean that the graviton (j = 2) cannot be a composite particle in a relativistic quantum field theory.
