Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On slowly rotating black holes and nonlinear electrodynamics   We discuss the solution to Einstein's equations for a Lense-Thirring inspired
metric describing a slowly rotating black hole coupled to nonlinear
electrodynamics. We show that different schemes of rotation for the black hole
exist; they depend on a parameter $\gamma$ defining the dependence of the
metric on the polar angle. The fulfilment of the complete set of gravitational
field equations and conservation laws implies constraints on this parameter and
the metric functions. The vanishing of $\gamma$ provides the Lense-Thirring
line element associated to any non-linear electrodynamics; the Kerr-Newman
metric for slow rotation arises when $\gamma$ is not vanishing, a feature that
emphasises the unique role played by Maxwell's electrodynamics.

13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int