A short remark (with a long title) on the universality of the quasinormal spectrum of near-extremal Kerr-Newman black holes

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S. A. Teukolsky and W. H. Press, Astrophys. J. 193
1974
Earlier work this paper cites.
S. Chandrasekhar, The mathematical theory of black holes
1985
Earlier work this paper cites.

S. Hod, Phys. Rev.D 78
Original
2008
Cited alongside, same era.
We use natural units in which G = c = ℏ = 1 G=c=\hbar=1
Cited in the paper.
Here M , M a , Q M,Ma,Q , and r + = M ± ( M 2 − a 2 − Q 2 ) 1 / 2 r_{+}=M\pm(M^{2}-a^{2}-Q^{2})^{1/2} are respectively the mass, angular momentum, charge, and horizon-radii of the black hole
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The parameter δ \delta is closely related to the angular-eigenvalue λ \lambda of the angular Teukolsky equation, see [ 6 ] for details [see, in particular, equations (2.7) and (6.3) of [ 6 ] ]
Cited in the paper.
M. Zilhão, V. Cardoso, C. Herdeiro, L. Lehner, and U. Sperhake, arXiv:1410.0694
Original
Cited in the paper.
On the other hand, the different overtones which compose the time-dependent gravitomagnetic signals are characterized by different
Cited in the paper.