Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic perturbations of black holes in general relativity
  coupled to nonlinear electrodynamics: Polar perturbations   The \textit{axial} electromagnetic (EM) perturbations of the black hole (BH)
solutions in general relativity coupled to nonlinear electrodynamics (NED) were
studied for both electrically and magnetically charged BHs, assuming that the
EM perturbations do not alter the spacetime geometry in our preceding paper
[Phys. Rev. D 97, 084058 (2018)]. Here, as a continuation of that work, the
formalism for the \textit{polar} EM perturbations of the BHs in general
relativity coupled to the NED is presented. We show that the quasinormal modes
(QNMs) spectra of polar EM perturbations of the electrically and magnetically
charged BHs in the NED are not isospectral, contrary to the case of the
standard Reissner-Nordstr\"{o}m BHs in the classical linear electrodynamics. It
is shown by the detailed study of QNMs properties in the eikonal approximation
that the EM perturbations can be a powerful tool to confirm that in the NED
light ray does not follow the null geodesics of the spacetime. By specifying
the NED model and comparing axial and polar EM perturbations of the
electrically and magnetically charged BHs, it is shown that QNM spectra of the
axial EM perturbations of magnetically (electrically) charged BH and polar EM
perturbations of the electrically (magnetically) charged BH are isospectral,
i.e., $\omega_{mag}^{ax}\approx\omega_{el}^{pol}$
($\omega_{mag}^{pol}\approx\omega_{el}^{ax}$).

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The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio