Rotational terms and quantum degeneracy in black holes
  It is believed that the first law of black-hole mechanics has no independent physical significance and acquires it only after identifying with the first law of thermodynamics. It is argued here that the first law of black-hole mechanics has a direct physical significance: not only the term $\Omega dJ$ but all its terms have the same mechanical meaning - the rotational kinetic energy of a black hole in real or in an internal space. Moreover, it is shown that the Kerr-Newman black hole is a system of non-degenerate plane rotators represented by the corresponding terms in the first law of black-hole mechanics. It is found that a degeneracy arises because the energy of a black hole does not depend on where an internal angular momentum of a black hole associated with the black hole area is determined on the horizon. 
Kostiantyn Ropotenko
gr-qc hep-th