Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fluid Black Holes with Electric Field   We investigate the gravitational field of static perfect-fluid in the
presence of electric field. We adopt the equation of state $p(r)=-\rho(r)/3$
for the fluid in order to consider the closed ($S_3$) or the open ($H_3$)
background spatial topology. Depending on the scales of the mass,
spatial-curvature and charge parameters ($K$, $R_0$, $Q$), there are several
types of solutions in $S_3$ and $H_3$ classes. Out of them, the most
interesting solution is the Reisner-Norstr\"om type of black hole. Due to the
electric field, there are two horizons in the geometry. There exists a
curvature singularity inside the inner horizon as usual. In addition, there
exists a naked singularity at the antipodal point in $S_3$ outside the outer
horizon due to the fluid. Both of the singularities can be accessed only by
radial null rays.

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The categories of this paper are: cs
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th